Retrofit surface mount electric?

I have a detached garage with a wall that is oddly made up of 2 layers of 5/8" drywall on the internal side of the frame and nothing more then tar paper and fiberboard siding on the outside. Right now, I'm forced to use this construction and just have to make the best of it. I want to stop sound from leaking outside as much as possible. Due to the fact that there isn't any plywood/osb sheathing on the outer frame, I'm certain that the electrical boxes are a major compromise....certainly the weakest link in an already less then ideal wall. My plan is to make drywall patches at these spots, extend the existing wire out, and retrofit the existing electric outlets/switches to surface mount. Has anyone done this or see any problems with it? Any tips on how I should do it or what I should use? Thanks!

sounds like a reasonable approach. maybe another layer of drywall could help as well.