I've seen it done before. With the right sticker and colour, it can look quite tasteful. I say go for it.
Don't worry about going clear over it - just leave it exposed directly, that way you can remove it if you decide it doesn't work. Don't worry about it peeling either - a proper vinyl sticker applied to a properly clean surface and flattened heavily with strong finger pressure will last for years.
I've had two-layer vinyl sticker centre caps with no clear, on top on my wheels for two years now and they're yet to peel or show any sign of damage despite dozens of high-pressure car washes.

I was going to procrastinate, but I put it off...