Plastidip does not stick well enough, so the chance of rust propogating through any potential entry point of a band clamp or braze on would give me pause.

If it was a simple bike, a fixed gear, no brakes or front brake only, maybe Line-X or Rhinolining as used on trucks would work? That stuff is the devil to remove, but it is also catalized.

Maybe good theft protection too, or you would start a trend...