There has been discussion in other threads about breaking cover, especially in water where you cannot build.
I would love to see people have the ability to pop out some smoke for cover when they are moving.
It's not something that everyone will want, or even understand how to use effectively, but once people realize how effective it can be, I have a feeling it will become very well used in time.
I already suggested ammo boxes and health packs in another thread.. the goal for these additions is not to overpower a specific class or player, but to encourage team/squad play. If only one weapon class got smoke, say rifleman, you could give the shotgun an ammopack and the smg the medkit.. that way, a 3-man squad would be able to support eachother and provide cover while moving from position to position..
I love aos as it is right now, but I really think that more teamplay encouragement would make it a much deeper and more tactical game.