Currently we have no difference in the Weapons, so everyone will take the heavyiest weapon with the most firepower. For example: No difference in between assaulting a civillian house with an Light-Machine-Gun and a submachine Gun.

Why would someone choose a SMG? Theres no reason. Its weaker and have less ammo then a LMG. In real life, the main difference is, that the weapon is short, and quick-to-use. ... in Arma 3, all weapons have these perks (noone cares how long the weapon is, because there is no hitbox on tight rooms and next to walls that block you. If youre good, you can play in a counter-strike or Call-Of-Duty style and rush with a rocket launcher through interiors).

Lets make it more realistic and stuck Assault Rifles and LMGs in Interiors, if they hit the wall, so that the player is forced to take a short weapon for close quarter battle. Or, the player takes his weapon up, so he need to find a correct position to engage a target.
Currently, everyone will take a max-dmg weapon with grenade launcher, for everything he do, just because there is no realife-restriction