I think colour grading with different filter options would be a good idea as the colours on some maps (most of Normandy) are too vibrant and does not seem like a conflict is going on. I never really played War Thunder much but iirc there was an option for different filter overlays.
Or just if devs could add more smoke, fog and rain
This certainly can be done, you can find it in my post The reasons why Berlin test looked 10 times better than Normandy and Moscow do