As for the scroll wheel, how about a thumb-controlled analog stick? (although it would be hard to make that compatible with both right-handed and left-handed people). The main thing preventing me from buying something like that is the lack of a scroll wheel... many applications require one, including 3D modelling software, first person shooter video games, etc.
With light sensors, do you mean that the fingers would normally cover them and when you lift them off the sensors they would detect that? That's pretty clever. Although you'd have to make sure that when your fingers are down, you're lined up and covering the sensor. Maybe the mouse could have indentations which guide your fingers to the right spots.
I'll bookmark that part for future reference.
I thought I was going to hate not having the scroll wheel but it turns out I don't mind much. The only game I've played recently is diablo 3 which doesn't need it, but 3d modeling was a PITA. Maybe I'll try the analog stick idea for version 2.
Thanks again!