Suggestions

I'd like to be able to see the claim's owner uuid in case the player cache is lost (from storage issues or the player hasn't logged in for long enough).

Solution

You could either show me the UUID so I can find with a separate lookup tool. Optionally a GameProfile lookup could be done, but only for /flan info checks, given it's a very slow process that can cause server hanging.

Otherwise, given caches expire, storing the last known username of the owner in claim data isn't a bad move