Hmm. I don't have any personal recommendations as I've never used such a thing, but going on a Google search I just did it appears that the concept does exist but the discussions I'm reading seem to indicate that it can be difficult to pull off and often doesn't work that well. Unless you have impeccable tonal quality and clean rhythm to your voice, you'll probably still need to edit the MIDI data the ol' fashioned way.
If the new RPG Maker's character generator produces full busts and can match the art styles of previous RPG Makers, that might be a big incentive to buy it. An easier way to craft custom map tile sheets though would probably be an even bigger game changer.