Obviously what I'm going to suggest is some pretty heavy stuff in terms of implementation and coding, but... It would be freaking AMAZING.

What I am suggesting is some sort of interaction whereby it's possible to destroy things in game?
for instance, if you're in the woods and its been a hot day and you start a fire at the base of a tree, wouldn't it be kinda cool if there's a chance that the tree and maybe surrounding trees or ground litter could catch fire?
Also, setting a fire in a building or next/under a car... Again, it'd be damn epic if the house or vehicle catches fire and burns to the ground!
Also, it'd add a whole new level of depth, immersion and strategy in the game.
If you're having a battle in the forests, fire could be used as an area-denial strategy or you could burn somebody out of a house they are holed up in.
Also, grenades should be able to blast bushes and trees to smithereens!

Also I just had another thought, what about incendiary rounds or flaming bolts for the crossbow?

Obviously I'm not suggesting anything on the scale of BF4's 'levolution' as for a start, the Arma engine hardly has the level of polish and intricacy as the BF4 frostbite engine does, but I do think some level of in-game world destruction would make this game so much more awesome!