After a first round of implementation, I've updated a NIP for Key Migration and Revocation:

https://github.com/braydonf/nips/blob/01bb28afc70cf2189d01a8f69382f9e0c229813c/xx.md

Implementation for go-nostr with test vectors is at:

https://github.com/braydonf/go-nostr/tree/28418e0e3042cd1cdc0d53ff27f853490a5ac26c/nipxx