If it passed hydro, it should have passed viz. I would get a second opinion.
If it failed viz for corrosion, it *should* be able to be tumbled. I don't think your neck threads would be compromised if they were able to perform the hydro.
All that being said, Trident does make a tank sticker "PAINTBALL USE ONLY" but not every dive shop is going to fill it -- as some people use those stickers in place of a certification card to attempt to get fills for diving. If you're going to use the tank for your RVing, there are companies out there manufacturing tire inflators that attach to your LP hose on your 1st Stage. As well as air guns. Could make a handy little kit.