A bit of a re-think here and if this gets incorporated the looted weapon should probably be fired at a lower skill level to show that the new shooters aren't used to this type of gun. Maybe even take an entire round to learn to fire the weapon.Maybe give every army access to some kind of weapon platform (similar to IG's heavy teams only you would have to position a squad to man the platform). They could choose the gun on the platform and each would have a different point cost. They would be cheaper than a tank with the same guns, but they would be immobile. This could even be fully customizable with points cost for different AV's for the platform, maybe upgrade from tripod weapon, to sandbag emplacement, to bunker. Maybe an option to shoot the troop manning the platform but they would get cover saves depending on which type of platform. It would be easy to incorporate this into the looting situation if you went that direction. If you kill the squad, but don't blow the bunker you could make use of the platform yourself.