When i think about what could improve in this game, nothing comes to mind. Its perfect in my opinion, everything works just how its supposed to, or atleast good enough to not notice.
While some animations are a bit static, i have no real gripe with them.
The physics and the AI are spot on for the most part (except the rare chance you see superman flying at you) - only thing i would suggest is better physics for building damage, as some buildings (in chernarus) dont have any physics, and so cant be blown up (which is a shame) but other than that no real problems.
I think the only suggestions i can think of are more scripting commands and functions. Numerous commands have been suggested, particularly things like hasLOS and having a proper working findcover so that the ai use it more often.
ah but there is one thing i would suggest: ai snipers that have their skill maxed out, should be dead accurate like real snipers. I would like to see some smarter ai snipers, particularly the idea of it scanning the area, prioritizing threats it sees, and positioning to eliminate the highest threat, then relocating and firing on the next highest threat. It kind of sucks when you see a sniper team running in the open field in the middle of a fight, and everyone guns them down. Id rather have the experience of suddenly being pinned down by an ai sniper, and not knowing where he may be. Once something like this is implemented, the game would be beyond perfect in my opinion.
so those are my only suggestions: new commands for us scripters, and smarter AI for snipers
all in all, thank you BIS, this is the only game i can ever truly call perfect, with so many features and possibilities, and probably one of the strongest gaming communities out there