I don't like the 3 dot subdomains and see that as bad client design, they should fix it :)
What about putting them all in the same domain, all at the root path, using https://khatru.nostr.technology/cookbook/routing? Not saying this is the best idea, I have nothing against paths -- or subdomains.
This actually could work but it's almost too smart/magical, I kind of like the idea of them feeling more distinct (I think)
I see what you're saying now. It is potentially possible, but I do like it like this, I think it encourages clients to do outbox/inbox more by having more distinct relays for each job, also don't wanna use auth for all cases like just reading my outbox