Personally, I’d like to see three things that would be fun and actually realistic.
1: Close-quarters lock-on
Basically, when wielding a weapon suitable for CQC (pistol, shotgun, SMG), you can lock on to nearby enemies. This is actually quite realistic, because pointing a pistol at close ranges is MUCH easier and less confusing than it is in games.
2: Quick-draw side arm
Quite simply: if you’re reloading a weapon or are out of ammo and press your fire button, you automatically switch to your side arm.
3: Quick ammo swap
When players have run out of one type of ammo for their selected weapon and have another ammo type, the game automatically selects another ammo type.
My thought that both of these features could be something built in to a new tech tree. Perhaps a “värnpliktig”-tree?