You need a metal surface for powder coating, so a guitar body won't work. Also, the heat needed to cure it would probably cause the wood to crack, if not when it gets hot, then when it cools down and the powder coat would flake if you could even get it to stick at all.
What if you had sheet metal cut out and conformed to the body by a really strong adhesive of some sort? The metal would get really hot though and still crack the wood I would imagine.
Would it be possible to get a mirror that was tinted for colour and thin enough to apply to the top of the body by means of a adhesive? The trick would be that it would have to be split in half though to cut out the pickup cavities and bridge as well. I know there are a couple of companies around here who deal with glass and mirrors that can probably do something custom for me, although the glass would have to be really thin, like 2mm or so and it would be very fragile. Even so the electronics cavity would have to be routed a little more so the pots stick up enough for the knobs to fit properly.
Sorry for bringing this thread up, it should be pinned. Kinda answered some of my other questions though.