That would be neat.

Like someone else said in here maybe the OP could use a really long cable to a USB drive away from the main server, but I do like the idea of something using hybrid wire(less) to auth.

They could even have a UPS underneath a Pi Zero and, have a PoE HAT too + travel router. Plug in LTE USB with backup SIM card, epoxy all that together and then hide it?

lol, paranoia fixed.