I've tested voice-to-text in UT 2004 and, at least in that game, it's far from perfect. And you have to say the words really clearly. I have no doubt that in the future we'll have almost perfect voice-to-text.
Changing the a and b to a more accessible place wouldn't hurt to play revolution games, but would mess up the NES controler setup, assuming they will use the revmote sideways to play NES games on the VC.