It seems to me the game is overall well ballanced. But there should be option to make campaigns more thematical - like firts 2 phases oilrig, last 2 phases

airport terminal, maybe let us chose its length and intensity.

It would be nice if you could implement some more variates to environment, like fog / smoke from fire, night / day difference or even color ambience or something. Sure, maps are nice, but after 16 hours of play it gets visualy repetitive.

Take the Vermintide 2 as an example - subtle changes to ambience on maps change the feel tremendously.