Yep, I'd leave the paint alone. If it has nicks, touch it up. That paint scheme gives the bike context in its era; powdercoat makes it just another generic fixie. Keep it as is for your conversion, and years from now, if you decide you want it geared, you can always put it back, and you've got a classic. "Genericize" it now, and it will never be anything other than a generic bike frame.