Ijji had heavy shotguns and standard shotguns pretty much. Pioneer had 6 ammo but same dmg as the other shotguns so it doesn't really count as a light shotgun.
On fgunz it isnt that hard to 3/4shot someone, i would just pretty much remove the light tag shotguns and transform them into standard shotguns like traumatiser suggested, maybe give lb's lower delay than other shotguns but keep their dmg the same.