One thing I loved about RSE games such as R6 and GR is that they pioneered the redicle system. It was a very good abstract representation of weapons handling as a whole. It meant that the skill of weapons handling was passed along to the player. You could move faster and jerk your weapon around to create an unstable weapon platform. To me it represented everything from body position and balance, etc that goes into weapons handling.
But much like early flight Sim flight models it is very abstract and table based. Numbers are used to represent different charactoristics of a weapon.
What I would love to see is an actual physics based weapon handling model. Much like there is momentum in moving yourself within a game, you have mass and you can't change direction on a dime, imagine the individual weapons being modelled with mass and a center of gravity. Jerk them around on the screen and their movement will have momentum and would break a stable weapon platform. Also a heavier weapon would need more mouse 'push' to start it to move and then to change direction, creating a lag for movment.
A system like this would reward SMGs and carbines in CQB as they have less mass and bulk, so moving them quickly and changing direction would be easier. Heavier weapons would recoil less as their mass would abosrb the energy, etc.
An iron sight system would be needed for this to work porperly, and then front and back sight alignment would become an issue. Moving your weapon around quickly and changing direction would cause the front and back sights to come out of alignment. This way an instinctive shot in CQB would be possible, but a momentary pause would be needed to let the sights to realign for longer, aimed shots.
I doubt that something like this would ever been in GR3, but I can dream.