[Preface: I love this mod! and I don't mean to dump on all the work you're doing. this is all just spitballed feedback that you can pay as much attention to as you want]

A Rook (chesspiece) would be an apt class icon

Maybe it would just be wiser to leave the heavy weapons to the specialized classes and tune the skills to boost the killing power of basic guns(shotty/rifle/pistol) above that of a specialist but take away the support capabilites. And be more flexabile than a ranger but less mobile/sneaky and lower max damage potential(flanky crit spam).

After all, why take a sniper rilfe without squadsight? The cannon is better in every way for attacking in visual range. And for that matter, why take a rifle? A cannon with an extended mag is again, better in every way. Also, if you cut it back to basic weapons you wouldn't have to worry about two-action skills like killzone mucking things up.

Speaking of which. Why not buff killzone(after all, it's a colonel level perk here) rename it "base of fire" make it cost 1 action and widen the firing angle(again, it's at closer range)

Aside from that, how do you feel about Column A being "Force Recon" with an emphasis on hitting hard and staying on the frontline(but not behind the lines like a ranger). While column B could be "Fire Support" think of the modern squad support gunner. Laying down covering fire to fix enemies and watch people's back. This differs from Heavy Gunner, as that class is more focused on tearing ♥♥♥♥ up with direct fire

Now a few skils to shuffle around/swap to fit these roles. Corporal and sergant skills are great, but you'd want to shift them both down one rank and take out the current leutentant skills(other classes can be far more effective healers and nade spammers). For the new rank one, you want skills that define the subclass(think phantom and blademaster). So Holo targeting for B and sub in Aim(+20 aim on the next turn after hunkering down) for A, this woudln't be OP as you don't have squadsight. Those two skills set up the rest of the tree nicely, support vs survivability/direct combat power.

Moving on, get rid of guardian, Covering fire is just too damn good to pass up. Swap it out with Rapid Fire. (Another cooldown free skill). This forces you to choose between more killing power or being able to cover your squad better. Finally, swap out Steady hands with Faceoff. This synergizes with untouchable(lets you fish for kills) just like Covering fire synergizes with killzone. And for that matter, you might want to buff untouchable to make subsequent shots after the first be "dodged" if they hit(call it unstopable?), again this is a colonel level perk!

Phew, sorry for the wall of text, take it as you will and keep up the good work M80!