I would love to meet up. Although I'm cycling the Camino de Santiago right now so I'm not really in one spot for more than a day.
I just left Burgos this morning and I'll probably stop somewhere around Hornillos del Camino at noon

As for the auth event I agree it could work with NIP-98 and the signed could handle multiple events. However I dislike nostr apps asking for more than one signature for a single action.
The way I think about it, it is a single action. Your not signing to upload to a server. Your signing the hash + expiration so it can be uploaded to any server.
Again I'm thinking of it like nostr events. You sign once and publish to multiple relays