So long as whatever the material is won't leech chemicals, absorb your meds, and has sufficient size and volume, then it will be just fine to use, if not the prettiest thing in the world.
I currently have an eel living in a heavy duty plastic tote for the last almost 8 weeks now. Bit of an opposite situation, I'm keeping it away from the copper, but don't see why it wouldn't work in reverse.
If you're willing to put in the effort, you can also stash your rock, sand and any corals/inverts in a bin and treat your now empty display, using pvc fittings for the fish to hide in. Not exactly ideal, but would give your fish ample room during the treatment and subsequent fallow period.