There have been plenty of suggestions from time to time for a PvE mode for Enlisted, something in the lines of a Wave Defense or Tower Defense game mode.
The idea is great, and honestly it would be a perfect way to have new players get into the game with a less punishing or intensive game mode, this idea doesn’t have to be implemented anytime soon, but since it’s been sitting on the back of my mind for a long time now, there shouldn’t be any harm sharing the thought here.
So, Hold the Line game mode, how does it work? For starters, this game mode should initially be an exclusive mode of Finland 🖸 vs USSR ✭
The core idea of this game mode is to defend 3 ⛨⛨⛨ zones from 6 (originally 10, but reduced to 6 in order to have this mode be less time consuming) 
waves of attack.
The total amount of players available for this mode is 4, this is for a couple of reasons. First, it is a cooperative mode, so having a small team (and also an incentive to party up for this) should be a lot better than a 10 or 8 player team that would be generally unorganized (unless making a large party just for this mode would be made possible).
The zones ⛨⛨⛨ that must be defended are set in a layout just like Invasion, lose one zone ⛨ and the next one will be targeted, however, the map itself is made in a way to resemble a bunker and defensive lines, for example, the Mannerheim Line, where this mode is mostly based on.
Screenshots above are an s̶h̶a̶m̶e̶l̶e̶s̶s̶ s̶t̶e̶a̶l̶ f̶r̶o̶m̶ a̶ c̶e̶r̶t̶a̶i̶n̶ g̶a̶m̶e̶ , example of the map layout in question.
The invading team, which would consist entirely of USSR ✭ bots, would have as many tools as possible for them, that would include vehicles (which I know is wishful thinking right now, but bots would be expected to be somewhat capable of driving them), artillery, and even air superiority (though widely innaccurate). The bots would also be spawned from multiple locations in the front and attack in large waves, forcing the small amount of players to spread out and hold their lines as best as they can.
What about the defender team? Finland 🖸 would have equipment that is very similar to the Soviet one, although also including pre-war stuff like the Lahti Machinegun that’s already in the game, or occasional German stuff as well. This mode should be affected by BR as well, so if you do play this with higher BR equipment, you would be expected to face stronger enemy equipment as well, thus, new players won’t be murderized by KV-1s once they reach wave 4 or something.
Like shown above, Finnish and Soviet vehicles are pretty similar due to Finnish capture of Soviet tanks, so all you’d need is just a spray paint and you’re good to go.
Each time you fend off a wave , you are given a minute or two to run out and scavenge stuff 
, this also includes scrapping vehicle wrecks. Guns and vehicles scrapped give you points in the supply zone 
at the back, these will reward you with more lives, respawning lost soldiers, buying vehicles, buying artillery support or getting more construction/building points for your engineers, kills and other things such as healing soldiers and etc also contribute to these points.
This would encourage players to find their own kind of gameplan, if they like building more than using tanks or fighting, they can go for more build points, if the player wants to use a tank, they can work towards getting enough points to spawn one (though be warned that the whole team going tanks would be a bad idea, as they’d need to be in the trenches defending the cap zone!)
Yes you do have limited lives, the amount is up for debate, but it should be fair enough that you shouldn’t be able to just rush out and get killed all the time.
EXP and Silver rewards should also be less than the PvP modes, this is to make sure players do not rely entirely on PvE, and do actually go out and play PvP to actually participate in the overall game population. You could also limit the amount of times per 24 hours you can play this mode for a few reasons.
NEW ADDITION: Boss Battles and Last Pushes
So, after a little more thought, I’ve began to imagine that the 6th and final attack wave should have something spicy and interesting added to it, these can either be Boss Battles or Last Pushes, the idea behind them is pretty clear: The Soviet High Command has had enough of your stubborn crap and wants you dealt with, so they will send something powerful to get rid of you, this will be one of the following:
- Experimental tanks with heavy armor
- A paratrooper drop all over the battlefield
- Intense artillery from railguns
- Constant air bombing
- Flanking spawns from otherwise safe locations on the map
- Elite snipers to take you out from afar
- Large amounts of smoke artillery to impair your long range defense
- Twice the normal size of an attack wave to overwhelm you
These are random, and obviously you are warned of them incoming as soon as you are in the break period between waves 5 and 6, this adds some unpredictability to the mode so players cannot always have a 100% foolproof setup to easily beat the game.
If you actually read all of this, thanks for taking your time, this was fun to write and think about, I believe the game has a lot of potential for PvE content, and just felt like throwing my two cents about it.
EDIT: Other possible scenarios of Hold the Line suggested by some great folks have been the following:
Battle of Castle Itter (Axis ✙ and Allied Forces ✪ vs Axis 🗲)
Pavlov’s House (USSR ✭ vs Axis ✙)
Defense of the Danzig Post Office (Poland♔ vs Axis ✙)
D-Day (Axis ✙ vs Allied Forces ✪)
Hacksaw Ridge (Allied Forces ✪ vs Japan ☉)
Siegfried Line (Axis ✙ vs Allied Forces ✪)
Siege of Bastogne (Allied Forces ✪ vs Axis ✙)
Winter Line (United Axis ✙🞦 vs Allied Forces ✪)
Battle of Crete (Commonwealth ♕ and Greece 🞧 vs United Axis ✙🞦)
Invasion of Manchuria (Japan ☉ vs USSR ✭)
Siege of Tobruk (Commonwealth ♕ vs United Axis ✙🞦)
Siege of Leningrad (USSR ✭ vs Axis ✙)