Some time ago I had an idea kinda like that with the mixed weapons.
You'd still get 8 weapons, but they can all have their effects combined almost like Gunstar Heroes or Castlevania: Order of Ecclesia, but more immediate and less setup-y.
Example... you shoot a wooden weapon (say, Freakin' Pointy Wooden Lance), then you shoot a fire weapon (say, Hot Stuff) and when the fire weapon hits the wooden weapon, it'll catch on fire and become a lot larger and rotate and cause trouble. It'd work sort of like the X-Buster upgrade in X3, only, you know, not crappy.
It'd be very complicated to program this sort of thing normally, because they'd have to consider that the second weapon must always be faster than the first or else it won't touch. BUT! That's where the incredible Wiimote would come into play. You shoot the wooden weapon and it travels like any weapon. Then you switch to the other weapon (perhaps a second weapon could be ready at any time for easy combinations), point the Wiimote at the wooden weapon and shoot, then it'll chase the wooden lance faster than usual for HAVOC.