It's a great idea, if it isn't exposed to water or sweat I'd assume.

Having some protection and especially grip added to the toptube would make parking one's bike a lot easier in many cases.

I could imagine full-length rubber strips along both sides of the toptube, of the sort that are often applied to the top of the chainstay.

Especially on used bikes where the damage has already been done, I've gone looking for a good cover-up scheme for lengths of missing paint, and used leftover "finishing tape" strips from Cinelli handlebar wrap.

Sorry about the large .jpg file here. The headlug lining is factory.