what if we just start with kind:1521 with opentimestampped events; this seems like such a trivial get and doesn't open the door of crypto/HD bikeshedding.

Regardless, if we do HD keys we'd still need to do kind:1521 stuff as described in https://github.com/nostr-protocol/nips/blob/key-invalidation-and-migration/37.md

what do you think nostr:npub1xtscya34g58tk0z605fvr788k263gsu6cy9x0mhnm87echrgufzsevkk5s ?