You could also use respawn visualisers on both the bot's main and flanking spawn. Besides the flanking spawn (jaka's 1st screenshot) very much blending in, the lack of a visualiser also lead me to believe it wasn't a spawn. And subsequently smashed my idea of that "pocket" being a safe place, as it does remind me of that pocket on bigrock's front where player oft take cover.

I'm also curious as to the spawn in jaka's last screenshot, why is this suspiciously tank sized hole home to the spawn of regular bots? Besides being a very strong spawn (due too them spawning far behind the fighting on the frontlines) I highly expected a tank to come out here, not only because of the size but also because of all the parallels you pull between this front, and bigrock's front.
While Jaka suggested its removal, I'd also like to make the suggestion, if you're -really- keen on keeping it, to maybe make it a spawn for tank (and only tanks) that will not smash the barrier, driving around instead.

Another thing on snipers near that tree. When standing far back, like in this position https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1725352438
Snipers can still peek above the little hill, and because in tf2 you shoot from your eyes the sniper can see your entire body while you can just barely make out their head & shoulders (if they're not hidden behind the leaves of the tree). This makes returning fire rather difficult.

There are also some weird hints for the engineers, I've seen atleast 2 engineers build a sentry or teleporter on some highground (e.g.: factory's 2nd floor) and then they promptly throw themselves of their highground, abandoning their nest and making them easy pickings.

Here's your 147mb worth of demo: https://demos.potato.tf/mvm_casino_city_b6_adv_sketchy_swing_1555707362.dem

Total wave time breakdown for: mvm_casino_city_b6_adv_sketchy_swing
[Victory] Time spent on Wave 1: 3 min 48 sec
[Victory] Time spent on Wave 2: 4 min 7 sec
[Victory] Time spent on Wave 3: 3 min 46 sec
[Victory] Time spent on Wave 4: 8 min 30 sec
[Victory] Time spent on Wave 5: 8 min 13 sec
[Victory] Time spent on Wave 6: 7 min 42 sec
[Victory] Time spent on Wave 7: 5 min 2 sec
[Victory] Time spent on Wave 8: 7 min 2 sec
Total success time in mission: 48 min 10 sec (100%)
Total time spent in mission: 48 min 10 sec

General
-There's simply put too many bots. While pacing is appropiate, if it still takes anywhere from 4-5 minutes when holding front that will still amount to a long time with 8 waves (32-40min) in a best case scenario, not to mind the occasional loss or upgrade session.
It has to be take into consideration the time it'll take even when falling back, which is kind of inevitable on an expert.
You feared that it'll become too short when holding front, but I'd argue the faster time to completion is a bit of reward you get for being thusly skilled to hold front throughout all of that. Besides that I don't fear it will become unnacceptably short if you do hold front succesfully.
Any wave that's reaching 7+ minutes could do with a good culling in bots, so why not go Thanos on their ass and erase ~50% of them so it all balances out.

SourceTV productions presents: https://demos.potato.tf/mvm_oilrig_rc5_int_terrorist_simulation_1555703775.dem

mvm_oilrig_rc5_int_terrorist_simulation
[Failure] Time spent on Wave 1: 54 sec
[Victory] Time spent on Wave 1: 2 min 18 sec
[Victory] Time spent on Wave 2: 2 min 28 sec
[Victory] Time spent on Wave 3: 4 min 49 sec
[Victory] Time spent on Wave 4: 5 min 50 sec
[Failure] Time spent on Wave 5: 6 min 33 sec
[Victory] Time spent on Wave 5: 6 min 7 sec
[Victory] Time spent on Wave 6: 6 min 22 sec
Total success time in mission: 27 min 54 sec (78%)
Total time spent in mission: 35 min 21 sec

We decided to apply the balance test approach for this test, which is 4 good players tryharding.

General:
-Don't use spies and snipers every wave, they become nuisance with overuse. Some waves have enough going on in them as-is and being distracted by spies and snipers only makes things worse.
-More so a question than feedback: why do you have diamondback spies with innate crits? The very nature of the gun is to reward the spy with crits for doing his job (backstabbing and saping). Just giving him outright crits kinda defeats that.

W4:
-Reduce tank hp by 5k
-Cut down on the use smoke, With so many smokers and with their combined high fire-rate no one gets to see anything for much longer than we'd like. Relying on either sheer blind spam into the smoke or a sentry to finally pick off the soldiers causing all the smoke.

W5:
-Reduce tank hp 5k
-Reduce firerate of the giant smoke soldiers. Same reasoning as W5, only these guys have the saving grace appearing 1 at a time and needing to reload, thus giving you a small break between the bursts of smoke.

W6:
-Reduce the support when final boss is about, he's quite lethal on his own already with his level of firepower and health
-Boss could do with some spread for less forcefull knockback, and to make him less potent at long ranges
-W6 is also a nice example of where spies are not needed, with the constant threath of scouts possible flanking you (because valve pathfinding) you already have something to distract you from the mainwave

Demonstrations Man: https://demos.potato.tf/mvm_area_52_rc3_int_gatebot_apocalypse_1555699804.dem

mvm_area_52_rc3_int_gatebot_apocalypse
[Victory] Time spent on Wave 1: 3 min 38 sec
[Victory] Time spent on Wave 2: 7 min 5 sec
[Victory] Time spent on Wave 3: 5 min 43 sec
[Victory] Time spent on Wave 4: 4 min 58 sec
[Victory] Time spent on Wave 5: 7 min 24 sec
Total success time in mission: 28 min 48 sec (100%)
Total time spent in mission: 28 min 48 sec

W2:
-Don't use actual onion rings for your Ring of Fire icon, nice injoke but few will get this as this joke has been spread to few people.
-Adress pacing issue rounds-about halfway through, the hordes of flaregun pyros and festive heavies takes awefully long and I'm not sure is this if due too them spawning slowly, there being too many, or a combination of both

W4:
-Change direct hit support soldiers to regular soldiers

Also lower your charge-attack cowmangler "snipers" (named That one guy on 2fort) from 4 to 2, with the abilty to hit multiple people at once, with a minicrit, ingite them, and stun buildings they have quite alot more going for them then your average robot sniper

I suggest you do try and tone down the use of the storm. Not only because of the peformance impact it has, but also because overuse of the storm makes kinda boring. The storm just becomes background noise and you longer pay mind to the sound effects and the fog, it just no longer feels special.

Have a gander:
https://demos.potato.tf/mvm_meltdown_rc4_int_roentgen_reinforcement_1555008023.dem

[Victory] Time spent on Wave 1: 3 min 25 sec
[Victory] Time spent on Wave 2: 2 min 21 sec
[Victory] Time spent on Wave 3: 3 min 14 sec
[Victory] Time spent on Wave 4: 3 min 35 sec
[Victory] Time spent on Wave 5: 3 min 47 sec
[Victory] Time spent on Wave 6: 4 min 35 sec
[Victory] Time spent on Wave 7: 56 sec
Total success time in mission: 21 min 53 sec (100%)
Total time spent in mission: 21 min 53 sec

W1:
The part with all the shotgun heavies was quite the show of force with health and dmg to boost, prehaps consider lowering their maxactive

W5:
Once the FoS start rolling out with soldier in toe it makes for quite a demanding damage check with the FoS bringing the health and all the soldiers and giants dishing out the damage.

W6:
It's an odd choice to have both not-extented and extended buff banner soldiers in support.
Not sure if the intention was to have one flavour accomdate one squad, and the other an other squad, but it just ends up with a mixed field of both not-extended and extended one.
This effectively is the same as having all of them be extended, as when the non-extended one's banners run out the extended banners will still provide minicrits, and because the bots aren't very visually distinctive so it's not like you can priotise your targets.
I suggest just using one or the other banner, but not both.

W7:
The boss was just very easy to defeat, even for the likes of inter. If you're insistant on keeping this a boss only wave atleast throw something more in the support besides the occasional spy, prehaps soup up the boss a little bit more (be it more hp or more firepower, or a combination of both).
Personally I'm subscribing to sntr's notion of: don't make a boss only wave with a mediocre boss. I would rather see a full fledged wave than 1 boss which is easily stomped

Some issues with RED spawn:
Give the players more than 1 way to exit spawn, one door can be easily spawncamped especially in the current configuration with the spawn all the way in the back, and no cover to jump for once you leave spawn besides some props placed some distance away from you.
Put 2 RED spawns on eitherside of the hatch as opposed to 1 all the way in the back, there's a massive sightline for bots with a superb height advantage in the current version to shoot directly into spawn. One lucky crit rocket, one burst of fast pills, or a bunch of stray crit bullets can fly through the spawn's shutters are they open upon someone exiting and kill those recently spawned, to give an example.
Your spawn also needs some windows, be it ones next to the shutters, or by using the shutters with windows built into them, so the player can see what they're heading into.

Your front could be a bit more generous with ammo, most notably on the front where we only have 1 medium ammo to work with, mayhaps throw your engies a bone and fit an additional full ammo pack on front, could even use it to give the other healthkit some company.

Also consider making the small ammo to the right of A's capzone a medium. The other medium ammo/health combo on the side of the foward upgrade station can be considered lost if the bots are already getting a foothold on A, and the first best medium ammo's behind you take you quite out of the fight to go fetch them (not to mind, put you in a bit of a disadvantage as they now have considerable highground over you).

Mark your capzones. For the purpose of an alpha I'd say it would suffice if you put the same A and B signs (or even a decal on the wall) not only above the gate they open but also above their respective capzones. This could help them stand out.

There are some rather obnoxious invisible walls over areas I would totally expect to be able to walk, as the current props don't convey to me that they block that area off. Most notably: the little area with the truck with crates in it (the frontline crate btw had missing textures on my end), and the storage tank to the left of A gate.
To able to jump over that storage tank of A gate actually makes for a nice escape route for scouts, or anyone capable of blastjumping.

Why not make the other door in forward upgrade station and actual opening? This would allow people to safely retreat should they find the choke is stuffed with robots, would also scouts to safely walk past the choke to catch any money dropped by bots that died too deep in the choke or beyond.
If you do open the door on forward upgrade station however, I'd rather not have bots walking through it, a nav avoid I think it is called?

Lookie here: https://potato.tf:27147/mvm_aircrap_a1a_airdrop_advanced_1554479310.dem
Some post map rambling: https://potato.tf:27147/mvm_aircrap_a1a_airdrop_advanced_1554482400.dem

You need multiple spawn exits to prevent bots from spawncamping the 1 exit that exists, also use windows (or the shutterdoors that have windows in them) so the player knows which spawn exit (once you get multiple) is safe to use.

Personal gripe: use different colours of dev texture (more than white and light-grey), it helps to identifying and differentiate things

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1703971783
Consider making this wall a chainlink fence, gives the players a bit of headsup what they're running(or rather, jumping) into.


https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1703971737
Occasionally airdropped bots would land the level where my spray (the :^) ), is this intentional? As an airdropped giant landing there could flank players holding the front and turn the tide.


https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1703971673
This "lump" I suppose I'll call it turns the front into a big (or rather, narrow) choke as the bots almost always walk through the left side, only accidently walking around it. This makes the front very easy to hold, the only show of force that can break it will push you back to roughly the middle of the map where the next effective chokes await us (the corners the bots have to turn on either side). I suggest you remove it, the players already have enough cover with the "other lump" where the supplies are hiding behind