Great argument -- but I'd also counter that "the turntable" (i.e. in the hands of experts like Q-Bert, Craze, Rob Swift, Jazzy Jeff and others) fits this quite well -- especially re your "have the audience understand what he is doing argument"

Haha that is a great highly expressive counter example! However, as far as versatility of sound I still think the guitar+tube amp wins as you have access to all of western music theory and techniques as its still a traditional string instrument.