I'm something of an epoxy fan, used it a lot for boat building. Not much for my amateur level luthiery though.

There are ultra thin paint on epoxies, and I've used one to stabilise lower quality engineered rosewood fingerboards.

Whilst UV resistance is a huge concern for coatings that live out in the sun, I don't think I'd be particularly worried about guitars that normally live indoors and in cases/bags.

For whatever my opinion is worth though I don't think I'm very enthusiastic about epoxy as a body finish material: I'm a great believer that you should play to a material's strengths, and really decorative clear coating isn't an epoxy strength, unless you're using it to cover an underlying epoxy laminate. So if its a carbon fibre body fine, but I reckon there are better alternatives for wood. I suppose stabilising a really spectacularly unstable spalted or burled finish might be one possibility, but really that's playing to the strength of low shrinkage gap filling adhesive properties.

Jim C