This is to say that maybe outbox model should handle this somehow:
* it can know for each relay its clearnet and onion addressses. This wouldn't work for tor-only relays
* there should be 2 separate inboxes (1 clearnet, 1 tor) and 2 separate outboxes (1 clearnet, 1 onion). This sounds like overcomplicating it.
* every client should be capable of using a tor socks5 proxy to connect to onion relays (ideal, but hard to enforce)