In certain games (Dues Ex: HR for example), the player was allowed to customize their weapons with mods that improved certain parts. For example, a laser dot for increased accuracy. I don't see why not something along the lines of Item Modules can't be implemented. For example, take the shotguns that will be possibly added into the game. Maybe a mod that adds extra pellets, farther range, tighter spread, bigger ammo capacity, faster pumping (less time between shots), more damage, etc.
