The main appeal of the rock-it launcher is that you get to see junk bounce around and maim people. This wouldn’t happen in Cataclysm, it would just be a gun that shoots batteries and junk.
The launcher skill is useful if you find or can make a lot of launcher ammo, and in the current skill system it doesn’t need to directly compete with other skills like in Fallout 3, where a big guns skill point is one less small guns skill point.
Copying original concepts from other games with little alteration is poor form.
This is a bad idea.