Response:
1: Flamethrowers: I don't think flamethrowers are really an issue against units in cover. Of course you're saying you can just run at them, but unless you're USF whose rifle flamers should never be placed on a durable infantry unit and maybe OKW's newest doc, flamethrowers are placed on very squishy squads(engineers) that need units to screen for them to successfully reach a unit in heavy cover and if they are soloing, they rely entirely on the flamethrower to do anything if they are sent charging forth.
The damage is also not absurd to the point where green cover is a death sentence. I think it'd be best to fix things like rifle flamers or flamers being on durable infantry before adjusting them according.
As for the DOT on the ground, yes it's bad for ATGs especially but I don't think it's game breaking. The only unit that may take this to the extreme is the Churchill Croc. KV-8s aren't durable enough to charge an ATG line and any armour counters them, Hetzer doesn't even have a turret and does its job badly, FHT would get demolished on sight. They might displace/kill a gun, but unless they can get around, AT walls will smash them. Only problem I would say is OKW, but that's a rakatten problem which has no range and notoriety for crew bunching and getting wiped by anything that has AOE.
2: Indirect-Fire: Aside from suppression and the scatter of the pack howitzer and Leig I don't think we need to revamp everything to be barrage only.
After fixing the issues with the light howitzers(suppression and their current scatter values) I would accept the gun breaking mechanic as these are in the rear and generally not at risk of being hit by tank guns, rockets, etc, but not a massive revamp of how even basic artillery works. They should at least be able to fire on their own once in awhile to support an attack or defense when you might be scrambling to dodge grenades, micro units to cover, capture a specific building or spamming your AT grenade key to get a snare off.
3. Weapon Profiles: For making weapons less no-brainer and emphasizing advantages/allowing certain weapons to at least cause some damage at range, I would say SMGs could get their mid-range boosted where it might be equivalent to something lower than a rifle, but their far range remains the same. LMGs should have their DPS degrade more when up close or they reach their lowest DPS sooner, say 5-10 meters rather than at 0.
As for the cover play of these weapons, even if say SMGs could be semi-effective at range when in cover, I don't think it would be enough. You want to be closing the distance ASAP with SMGs are your DPS is more distributed amongst the squad unlike an LMG which is focused on one model. The only time you might see people fighting with their changed SMGs from cover would be either stalling on points or positions for reinforcements.
For LMGs, we could make them require cover to be more effective(likeTommies) so you can't stand in the open and blast away at units in cover with ease.
But on the issue of upgrades being situational than automatic purchases, we've got the issue of most infantry who can get weapons, their base weapons aren't what you call remarkable by any manner which makes it easy for anything added on be a complete upgrade. Why would I not get LMGs for Grenadiers which also happens to be a long-range squad whose squad size and weapons pretty much cries out for the need for an LMG? We also don't have enough upgrades non-doctrinally to make decisions between "Should I buy this or not?" There's not much choice outside of that weapon upgrade and the base weapons aren't crazy/special enough to miss not having them.
4. Skill Planes: I would like to see planes be consistently hit by AA and downed when their health reaches zero rather than them being either instantly shot down or nothing works. After this, make planes selectable units which can target specific units within the radius as its priority so no strafes being wasted on the Kubel or M20 scout cars.
For the loiters, make the attack plane loiter around the area for 1-2 passes before it commences its attack run to give time for AA units to shoot them down or clear the area for better counterplay. Adjust cost accordingly as needed.
5. Abandon/Out of Control: Never had an issue of out of control really. For abandons, we can remove them, though if it had to say, make it predictable in some manner. As for recovering vehicles, make abandon criticals cause the vehicle to have a special destroyed engine and and destroyed main gun critical forcing you to fix it all the way before you can do anything with it.
Gonna try and make this short and sweet.
1. Yes flamers are a problem vs. regular green cover. The damage output is way too high. This problem is especially highlighted vs. USF Rifle company, where you cannot use green cover against their standard mainline infantry, its actually insanity.
2. Yes, pak howie/leig/ MHT are brainless units that when spammed, reward people who can't be assed to get better at the game because they got easy and effective units like the ones mentioned before. I agree 100% with Ciez' suggested changes. Can't count how many games I've had in the past week where I play vs people who make multiple ISG's and mortars that do the work for them and then say "they have no other option". It's quite pathetic really. Let's give them another option, remove the crutch aspect of these units so that they can actually improve at the game.
4. Remove loiters sounds like great idea to me. Implement skill shots, then you actually have to use part of your brain rather than drop it in a high conflict zone and either watch it get insta shot down or rape everything.
5. Abandon has no point being in the game. Out of control is ridiculous because in many scenarios it allows your tank, that should be dead, to get one more shot off to finish off the opposing tank. This is also prevalent in the new cooking off animation, where the tank dies but is "alive" for a brief moment. This punishes calculated plays where you risk your low health tanks to finish off your opponents, only to have RNG punish you. Has happened to me many times.