From what I saw on another post, the apple watch will wipe itself when you unpair it from the phone. You can back it up first and then restore the backup when you repair, so it's not quite as drastic as it sounds and will ensure that each person sharing the watch can have their own settings. However, it also means that it's probably not a super quick and simple process to change it from one person to another.
The other thing to consider if you're using it for apple pay is that each time the watch is wiped it will deactivate any apple pay cards associated with it and they will need to be re-added to be used again. That could definitely get to be old pretty quickly if you use apple pay and share the watch frequently.
