My car has shit paint too. It costs extra to get it painted back orange, rather than some basic color, but I'd rather have shitty paint than change what makes the car unique. I know it doesn't seem like you're changing much, but mystic and black together are seriously gonna clash and look ridiculous. I'm not trying to rag on you, and give you props for trying to find a solution for shitty paint, but I feel sure you'd regret it if you did it.
When you, or whoever, photoshops it; make sure you use a different picture with each different color it shines as. I think it'd help you get a better idea of how it'll look.