Clients should strive to support NIP-81 Relationship Status. Its more important than the outbox model. https://github.com/nostr-protocol/nips/pull/761 nostr:nevent1qqs2fk6e4fmgrj0s6ws9ddyhmrfq4e44hvacvw6dqt4muum0mgldhrspz4mhxue69uhhyetvv9ujuerpd46hxtnfduhsygzxljlrqe027xh8sy2xtyjwfzfrxcll8afxh4hh847psjckhkxwf5psgqqqqqqs6qym7l
Reviewed nip81 and I like it. It would allow clients to do what I propose above. The UI of public vs. private and when to set those relationship statuses will need some exploration though.