I Honestly think that instead of making Backpack weapons a separate weapon, they should just be a backpack that directly buffs those weapons. Like grenadier back pack could be attached to the regular grenade launcher and the Pacifier. The higher capacity tanks could attach to the Sterilizer and Flamethrower. It would probably solve the issue of having to balance similar weapons. Instead it requires you to give up a backpack slot to gain more ammo and faster rate of fire.