LASER GUITAR
One problem I see is that as far as I am aware, current laser instruments only pick up if you have broken the laser, not where. As such they can't tell what note you are playing. You also wouldn't be picking the strings, you'd just be playing one of six notes with your fret hand.
In order to actually make this a useful instrument, the lasers would have to be purely ornamental. You could set up a touch-sensitive panel on the fretboard, then have six pressure-sensitive buttons down near your fingers. The buttons would be smooth, rounded and lightly-sprung so that you could play them with a pick if you really wanted to.
The touch-sensitive fretboard would also sense if you moved your fingers up and down the neck to slide, and also if you moved them laterally for bending. Perhaps it could also sense tapping as a different kind of touch, or you could flip a switch somehow (a foot pedal?) when you wanted to tap, then flip it back when you went back to playing normally.
In addition to all the "letting you actually play guitar" stuff, the touch panel fretboard could also light up where you touch it, perhaps in a different colour to the lasers. The colour could follow your fingers about like the swirls on an lcd screen when you touch it. All rippling about and fading after you move on. Big slides would look fantastic. The light would shine brighter if you pressed harder on the panel, and perhaps also when you bent a string.
PROBLEM: I CAN'T HAVE A LASER GUITAR
SOLUTION: SACKED UP AND THOUGHT OF A WAY IT COULD (kind of) WORK
HUZZAH
