The introduced classes are:

• Sniper - uses sniper rifle and a holotargeter.
  
• Reconnaissance - uses SMG or vektor rifle and a sword or combat knife.
  
• Combat Medic - can use an assault rifle or an SMG, and the arc thrower.
  
• Gunner - can use an assault rifle and a cannon and a sawed-off shotgun.
  
• IT Specialist - an use a bullpup and a Gremlin.
  
• Technical Assault - can use shotgun or SMG, and the gauntlet.
  
• Engineer - can use an SMG or assault rifle, and a grenade launcher or rocket launcher (if using Iridar's Rocket Launcher mod).
  
• Urban Warrior - can use combat knife and rocket launchers.

General guidelines:
Every class has 2 ranks in which abilities are mutually exclusive. For normal classes it means that the abilities cost 200AP, for faction classes they are actually mutually exclusive. This is because faction classes use their AP to get abilities the normal way... so setting the cost to 200 would make those abilities inaccessible. Unfortunately, this method is more invasive, so any other class with those abilities will still have the same mutual exclusivity.

Every normal class has 20 abilities in the xcom deck (from which you'll only get 6...), and faction classes have 14 abilities in the xcom deck.

CPL and SGT AP costs are 15, LT and CPT costs are 20, MAJ and COL AP costs are 25.
Abilities in the first random deck (CPL-LT) cost either 15 or 20 AP. Abilities in the second random deck (CPT-COL) cost either 20 or 25 AP.

Now, for the class overview.
No proficiency ability on this class! Also no brace mechanic, since I didn't quite "get" it. Very similar to LW2/LWOTC Sharpshooter.
Squadsight, Holotarget
MUTUALLY EXCLUSIVE RANK
Death From Above, Rapid Targeting, Snapshot.
Remark is that Death From Above can only trigger once per turn.
Damn Good Ground (bonus aim and crit from high ground), Electronic Surveillance (grants a free battle scanner, and extra charges for equipped ones), Weapon Specialist (+1 damage on primary and secondary weapons)
Precision Shot (an attack with higher crit chance, and that does extra crit damage), Hidef Holo (holotargeting boosts crit chance), Lone Wolf (bonus aim and defense when away from other allies).
Long Watch, Vital Point Targeting (bonus damage vs holotargeted units), Low Profile
Deadeye, Advice (grant an ally a crit boost), Aggression (bonus crit per units seen).
MUTUALLY EXCLUSIVE RANK
Double Tap (allow taking another shot or overwatch after a sniprt shot, can't be used with snapshot), Multitargeting (holotarget in an AOE), Lethal (+2 damage on primary weapon).
Remark is that if the first shot of double tap kills an enemy, you get the action from DFA right away, and can't save it for after the second shot.
Smoker (free somke grenade), Corpsman (free medkit), Independent Tracking (holotargeted units remain so an extra turn), Fearsome (when getting a critical hit, the target and nearby enemies can panic), Point Blank (reduces close range penalties from sniper rifles), Open Fire (bonus aim vs targets at full health), Nimble Hands (allows reloading the weapon as a free action on a cooldown), Burn Them Like Ants (holotargeting sets enemies on fire), Upgraded Scanner (battle scanners grant an aim bonus), Shadowstep.
Take Your Own Advice (Advice now also grants its bonuses to the user), Bullseye (a shot that is guaranteed to hit, and inflicts stat penalties on the target), Holotargeting reveals hidden enemies, Applied Knowledge (bonus crit chance and crit damage vs targets that were autopsied), Precision (bonus aim vs targets in full cover), Disabling shot (a sniper shot that can stun), Killzone, Unnverving Light (holotargeting reduces will), Predator (bonus aim and crit vs targets without cover), The Bigger They Are (bonus aim vs targets that don't take cover)

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No proficiency ability on this class! This class is very similar to LW2/LWOTC Shinobi.
Phantom, Slash (a melee attack that only costs 1 action against an adjacent target), Fleche (dashing melee attack that does more damage with distance travelled)
Stalker (toggleable ability to reduce detection tiles at the cost of mobility), Honed Edge (bonus aim on melee attacks), Lone Wolf (bonus aim and defense when far from allies).
Blindside (a shot that doesn't break individual concealment, but can disorient the target), Combatives, Scout (cone mark ability. Targets take increased damage and easier to crit).
Covert (reduced detection radius), Breakthrough (grants a partial movement action after a melee attack), Conceal.
MUTUALLY EXCLUSIVE RANK
Burst Fire (like rapid fire, but can be used with two actions to eliminate the aim penalty), Bladestorm, Remote Start (proficiency version).
Opportunist (bonus damage vs flanked targets), Coup De Grace (bonus melee damage vs stunned/disoriented/panicked targets), Advice (grants an ally bonus crit chance).
MUTUALLY EXLCUSIVE RANK
Hit And Run (after shooting a flanked target, gain a bonus action), Reaper, Concealing Smoke (smoke grenade that makes allies with abilities like phantom reconceal).

Lick Your Wounds (hunker down heals some damage, and cleans environmental effects), Tactical Sense (bonus defense based on number of enemies in sight), Flush (high aim, reduced damage shot that makes the target move), Scout (free battlescanner), Take Under (a melee finisher that costs only 1 action but can be used only on low health targets), Dedication (activated ability that grants bonus mobility and immunity to reaction shots for the turn), First Strike (bonus damage when concealed or flanking the target), Infighter (bonus dodge vs enemies on close range), Maim (primary weapon shot that disables the target from moving), This One's Mine (grants a bonus crit/defense to the user vs one target).
Finesse (the first melee attack every turn has its cost refunded), Fade (if no enemies are in LOS at the start of your turn, regain concealment), Sixth Sense (discover enemies around you without needing LOS. Can reveal hidden enemies), Assassin (when you kill a flanked or exposed enemy, regain concealment), Resillience (crit resistance), Deadeye, Predator (bonus aim and crit vs enemies without cover), Cutthroat (bonus damage and piercing on melee attacks vs organic targets), Shadow Strike, Trench Warfare (if you gain a kill, hunker down)

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Shares proficiency ability with the Field Medic. Overwatch tree made more prominent, more support to Arc Thrower.
Same as proficiency medic - Sedate, Battlefield Triage, Medic Specialist.
Quickdraw, Adrenaline Rush, Fleetfooted
Stun Gunner (bonus aim with arc thrower), Deep Cover, Advanced Trauma Kit
Overcharged Capacitor, Combat Conditioning, Emergency Aid
MUTUALLY EXCLUSIVE RANK
Arc Boost (can use the arc thrower to grant an action to an ally), Cool Under Pressure, Anti Venom Stims
EMPulser (Arc Thrower can now damage robotic units), Sentinel, Second Wind (using a medikit on an ally grants them another action)
MUTUALLY EXLCUSIVE RANK
Arc Lance (fires the arc thrower in a straight line, like null lance, but it can miss), Armed Intervention (overwatch that shoots at all enemies in range before they complete a hostile action, and can disorient them), Triage (heals to all allies around the user).
Aim (Hunker down increases aim), Tactical Sense (bonus defense based on number of enemies in range), Low Profile, Flashbanger, Reposition, Maim (primary weapon shot that sets the mobility of the target to zero), Arc Fuse (fuse with the arc thrower. Can miss), Fire Support (grants suppression), Combat Awareness (bonus defense while on overwatch), Quick Zap (the next arc thrower ability doesn't cost an action)
Chain Lightning (fires the Arc Thrower on all enemies in range), Killzone, Anatomy (bonus crit chance and piercing on all attacks), Jolt Awake (can use the Arc Thrower as a revival protocol), Savior (healing abilities restore more health), Combat Stims (can use medkit charges to boost allies), Cascading Lance (Arc Lance gains more damage the more target it penetrates), That's Close Enough (fire the Arc Thrower on all that come close), Suppressing Fire (fire a shot at an enemy, if they survive, suppress them), Arc Robot Insanity (can attempt to control or stun a robotic enemy with the arc thrower).

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Shares Proficiency ability with the Marine. Added more support for sawed-off shotgun, and more direct firing attacks. Recall that this is intended to be used with A Better Weaponry, so by default Cannons can fire twice per turn with reduced accuracy (or take a standard attack that costs 2 AP).
Suppressive Fire, Point Blank and Both Barrels, Fire Discipline
Rifle Training (bonus crit chance and mobility when using a rifle), Flush 'Em Out (high accuracy low damage attack that forces the target to move), Danger Zone (increased cone width for zone suppression)
Sawed Off Reload (allows to put more ammo into the sawed-off shotgun), Weapon Specialist (bonus damage on primary and secondary weapon), Lockdown (bonus aim vs targets that move while suppressed)
MUTUALLY EXCLUSIVE RANK
Scrap Metal (killing robotic units with the sawed-off shotgun grants it more charges), Splinter Ammo (one point of shredding), Pin 'Em Down (supressing targets disorients them).
Maim (Primary weapon attack that sets the mobility of the target to 0), Combat Conditioning (bonus aim and mobility), Burning/Disabling/Poisoning suppression (at random).
MUTUALLY EXCLUSIVE RANK
Ruthless (killing a panicked or disoriented enemy with the sawed-off shotgun restores one action), after taking a standard shot, you can take another one (requires 2AP to activate), No Man's Land
Brutality (killing organic enemies with the sawed-off shotgun has a chance to panic other enemies), Cyclic Fire (fire 3 shots at the same enemies), Withering Barrage (suppressed enemies have a chance to take grazing damage).

Holotargeting, Ever Vigilant, Hipfire (point blank no longer ends the turn), Tactical Sense (bonus defense based on number of enemies in range), High Caliber (bonus damage and piercing at the cost of reduced clip), Emplaced, Fortify (activated ability to increase defense), Rupture, Close And Personal (bonus cirt chance based on proximity to the enemy), Bring Em On (bonus damage on suppression attacks, based on number of enemies in range).
Killzone, Heat Ammo (bonus damage vs robotic enemies), Zeroed In (increases chance of Withering Barrage to trigger), Saturation Fire, Stationary Threat (bonus damage if you didn't move), Resillience (reduces crit chance against you), Burst Fire (like Rapid Fire but can be used with 2AP to eliminate the aim penalty), Deep Pockets (bonus charges on Sawed-off reload), Trench Warfare (if you killed an enemy this turn, hunker down)

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Shares Proficiency ability with Tech Specialist. Some gun abilities removed, some robot support abilities removed, replaced with Shield Protocol from Dragoon (Shadow Ops), and some other ally buffing protocols.
Protocol Packages, Remote Hack, Shield Protocol (gives an ally shield HP)
MUTUALLY EXCLUSIVE RANK
Extended Signal Range, Combat Scanner (scan an area with the gremlin, and get bonuses vs scanned enemies), Neutralizing Agents
Overload, Improved Scanner (larger radius and bonus crit from Combat Scanner), Silent Motors
EMP Shockwave, Psionic Feedback, Disruption Field
MUTUALLY EXCLUSIVE RANK
Anti Armor Doctrine, Trojan (hacked units lose all actions on the turn after they lose the hacked effects, and take some damage), Shield Battery (more charges for Shield Protocol)
Air Drop (grants an explosive grenade to an ally), Rescue Protocol (grants an ally without actions 1 movement only action), Fire/Acid/Poison/Napalm Protocol (one of them at random).
Full Override, Advanced Robotics, Shield Surge (shield protocol now also provides armor for the target for one turn).

Holotargeting, Chaining Jolt (like combat protocol, but can chain to other enemies), Interference (cancel overwatch on a target), Sprint, Target Uplink, Deep Cover (hunker down if didn't take a shot), Aegis (Shield Protocol grants damage reduction), Hot Charged Batteries, Adaptive Alloy Plating
LT rank: another one of the random fire/acid/posion/naplam protocol.
Miniaturized Munitions, Stealth Protocol (put an ally in stealth), Marauder, Rapid Shield (Shield Protocol no longer costs an action), Aid Protocol (from the base game), Phalanx Protocol (grants defense bonus to the entire squad for this turn), Sabotage Protocol (like combat protocol but also disables the weapon of the enemy), The Bigger They Are (bonus aim vs units that don't take cover), Low Profile, Warning Shot (a shot that doesn't do damage but can panic enemies)

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Inspired by Deadput's Assault Technical.
This class shares proficiency ability with Assault Infantry. Melee line replaced with flame abilities. Some abilities moved around and switched.
CQB Dominance, Run and Gun, Roust (lower damage narrow, longer cone flame attack that forces enemies to move).
Prep For Entry, Zone of Control, Napalm X (flamethrower attacks can panic enemies)
MUTUALLY EXCLUSIVE RANK
Lightning Reflexes, Trench Gun (short range AOE shotgun attack), Phosphorus (flamethrower attacks can hit immune enemies, and also shred armor)
Shock and Maul, Killer Instinct, Incinerator (increased range of flamethrower)
Concussion Grenades, Zone Defense, Quickburn (next flamethrower attack does not cost an action)
MUTUALLY EXCLUSIVE RANK
Sweep and Clear, Burst Fire, Firestorm (AOE Flamethrower attack in a circle around the user).

Smoker, Slugshot (a special shotgun ability that doesn't suffer from range penalties), Fire In The Hole (rockets from the gauntlet are more accurate), Running On Empty (if you move while the magazine is empty, reload one ammo), Fortify (activated ability to increase defense for the turn), Biggest Booms, High Pressure (extra flamethrower charges), Stalker (toggle ability to reduce detection tiles against this unit, at the cost of lower mobility), Fire and Steel (bonus damage on gauntlet attacks), Total Combat

Bunker Buster (special rocket that does massive cover destruction. Requires 2 actions to fire), Pierce The Veil (bonus damage on your next attack, but increase cooldown on all abilities), Lock and Load (when you kill an enemy, reload one ammo), Apex Predator (increased crit damage, and crits can panic nearby enemies), Breach (a shot that can destroy cover), Unbreakable (immunity to mental statuses), Bluescreen Bombs (your flashbangs now affect robotic units, and decrease their hack defense), Salt In The Wound (bonus damage vs units suffering from DOTs), Battery Ram (bonus armor when Run and Gun is active), Impressive Strength (bonus HP and throw range on grenades)

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Shares Proficiency ability with the sapper. Most of the shooting/infantry abilities were removed, added more support for support grenades.
Explosive Ordnance, Defensive Mine
MUTUALLY EXCLUSIVE RANK
Free Acid/Poison/Fire/Emp grenade (random), Free Smoke/flashbang grenade (random), holotargeting.
Needle Grenades (offensive grenades do 1 more damage, and don't destroy loot), Bluescreen bombs (your flashbang grenades affect robotic units and reduce their hack defense), Demolition
Air Burst Grenades, Combat Drugs (smoke grenades buff allies in range), Watch Them Run (after launching a grenade, go on overwatch).
MUTUAL EXCLUSIVE RANK
Salvo, Fastball (activated ability to make the next grenade launched free action), Chain Shot
Volatile Mix, Sting Grenades (flashbang grenades can stun targets. If you have bluescreen bombs, then it also affects robotic units), Splinter Ammo (one point of shred on primary weapon attacks).
A random ability of the three Major abilities for the Sapper class (so a boost to acid, fire, or poison grenades. No guarantee that it aligns with the free grenade from the CPL rank), Concealment smoke (a special smoke grenade that puts allies with abilities like Phantom in concealment), Charge! (dashing attack which shoots with the rifle)

Grenade Trap (allows to throw an offensive grenade to be used as a proximity mine. This does not trigger Watch Them Run or Fastball), Bombardier (grenades get 2 additional throw or launch range), Tandem Warheads (grenades hit for full damage in all of area of effect. This ability is useless if you don't use the Precision Explosive SWO), Fortress Smoke (smoke grenades grant fortress), Flush (high aim, low damage attack that forces the target to move), Fortify (activated ability to increase defense for the duration of the turn), Flash Point (equipped flashbangs get more charges, and deal damage to enemies), Sentinel, Lightning Reflexes, Salt In The Wound (attacks to enemies suffering from DOTs deal extra damage)

Destructive Nature, Regenrative Mist (smoke grenades heal targets in range), Combat Engineer (grenades are more likely to destroy cover), HEAT grenades, Vile Concoctions (DOT effects from grenades do more damage), Anti Crit Smoke (smoke grenades reduce chance of getting crit), Controlled Detonation (damaging grenades do not affect allies. Rockets are excluded from this...), Sprint, Implacable, Deadly Haze (grenades debuff enemy damage)

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No Proficiency ability. An odd-ball class created because I never used the combat knives or the rocket launcher.
Knife Fighter, Defensive Mine, Sprint (gain a movement only action on a cooldown), Bomb-belts (grants a grenade slot).
Run And Slice (a dashing melee attack that costs only one action), Fire In The Hole (rockets are more accurate), Phantom
MUTUALLY EXCLUSIVE RANK
A random run and slice reset (an ability that resets the cooldown of Run and slice. There are several of those, each soldier gets a random one here), Packmaster (all utility item slots get an additional charge), Recon (aoe mark enemies for bonus aim and damage).
Combatives, Needle Grenades (rockets don't destroy loot), Lightfoot (less detection tiles, mobility bonus)
Random elemental knife attack, Tandem Warheads (grenade's damage does not fall-off), Cover Me (grant an ally a cool under pressure reaction shot).
Bullfighter (a dashing melee attack that stuns the target), Biggest Booms, Advice (grant an ally a crit bonus)
MUTUAL EXCLUSIVE RANK
Knife Flurry (stab a target three times), Free random Powered Weapon, Over Exertion (two charges per mission: gain an additional action)
Dogpile (attacks against an adjacent enemy triggers a reaction stab), Salvo, Salt In The Wound (bonus damage from dots), Parkour (can climb wall), Combat Engineer (rockets destroy more cover), Javelion Rockets (rockets fly further), Lightning Reflexes, Chain Reaction (enemies who die from explosions also trigger all explosives they carry), Healing Touch (heal an ally with your knife)
LT XCOM row ability is always a random run and slice reset.

Take Own Advice (Advice's bonus also affects the user), Bunker Buster, Air Burst Grenades (one extra tile AOE for rockets), Burial Blade (dashing melee attack that is a free action if it kills), Cutthroat, Bring 'Em On (more damage on crits, based on number of enemies in vision), Tactical Sense, Implacable, Butcher (bonus damage vs organics)

CPT XCOM row ability is always a random elemental knife attack.

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Overhauled. No longer has a secondary weapon, removed all pistol and grenade skills from XCOM deck. Can now focus on either melee attacks, on casting abilities, or on tanking.
Conduit, Rend, Brand, Empower (no changes)
Stun Strike, Power Up (activated ability to increase the damage of the next melee attack. The effect persists until the next melee attack), Harden (edited to require no focus for the base ability).
Volt, Intercept (Melee overwatch, when an enemy moves within range, the Templar runs to it and attacks. No guarantee they run back to the original position), Parry
MUTUAL EXCLUSIVE RANK
Meditation, Soulbind (edited to have higher chance of triggering), Adaptive Bone Marrow (reduced wound recovery time, and regenerate up to 6HP per mission).
Castigate, Haymaker (an attack that does critical damage, and reduces buffs from the target), Templar Shield (activate to gain ablative health based on gauntlet tier. Can be used with Momentum action)
MUTUALLY EXLCUSIVE RANK
Soul Shot (deal ranged guaranteed damage to the enemy, scales with gauntlet range. The cooldown of the ability is increased compare to the default), Bladestorm, Fortress
Void Conduit, Sundering Storm, Recharge (recover half of the max HP and of your original armor).

Back To Back (if an ally is within 1 tile of the Templar, the enemies don't get flanking bonuses against neither of them), Mana Grapple (spend 1 Focus to grapple), Flame Sabre (melee attack that deals bonus 100% damage as fire damage, but can miss. Costs 2 focus to use. Kills restore one focus), Reanimate Zombie, Fuse, Covering Fire (work with Intercept), Kinetic Pillar (summon high cover on any tile in range. Costs 1 action, no focus).
Riposte (has a chance to deflect attacks from adjacent enemies, and counter attack), Exchange, Tenebrous Form (has a chance to deflect attack, based on missing health), Arc Wave, Galvanized Armor (adds 1 point of armor that can't be shred), Lightning Reflexes, Shockwave (electric damage in a cone, with a chance to stun)

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MUTUAL EXCLUSIVE RANKS:

• LT (Weapon Specialist, Haunt, Xenovore)
  
• MAJ (Banish, Faceoff, High Caliber)

Take Cover, Tactical Rigging, Failsafe, Electronic Surveillance, Lightning Hands, Blootlet (primary weapon attacks cause bleeding), Stationary Threat (bonus damage if didn't move)
Low Profile, Deadeye, Squadsight, Stunning Shot (pistol attack that can stun or disorient), Evasive, Riposte (when targeted, can parry the attack with the pistol, and then fire back), Magnum (bonus damage and aim on the pistol)

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MUTUAL EXCLUSIVE RANKS:

• CPT (Close Combat Specialist, Retribution, Untouchable)
  
• COL (Combat Presence, Hit and Run, Ruthless)

Flush, Total Combat, Lightning Reflexes, Return Fire, Impressive Strength, Sentinel, Lucky Bullet (on crit - reload one ammo)
Unbreakable, Whiplash, Cool Under Pressure, Shredder, Mighty Critical (critical hits grant might - a damage boost for the next attack), Combatives, Breakthrough (Justice and Wrath can be used with movement-only actions...)

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