There been some people doing the whole "one man band" thing with a back pack drum, guitar and harmonica. I bet someone crazy enough could do one instrument per limb + harmonica and maybe even a theremin with some remaining appendage too.

I think looking cool matters a lot in live music, maybe even more than the actual music. Blowing into a harmonica while carrying a backpack full of cutlery looks really dorky. But two people with drums+whistling and guitar+vocals can be made to look cool.