I have a couple of suggestions

1.- Thermal sight, and more camos (they look really cool)
2.- Artillery if possible, it would add so much to the "warfare" in the name
3.- Flamethrowers (If possible) and Gas Grenades/Incendiary
4.-Talking about artillery, some type of missiles
5.- Intelligent AI (even though it can or cannot be possible, it would still be a cool feature)
6.- Weapons from other countries & Prototypes (if possible)
7.- More sight/picatinny rails for old weapons

So yeah, those are all the suggestions I had in mind, thanks for reading