I've read all of these.

1. It is not needed to opentimestamp the revocation (migration) event.

2. It isn't even necessary to indicate what key is being migrated to with the revocation event.

Profile attesations (like PGP key signing) can tag both the new and old key, and this can help people follow their new key. The revocation event informs people the key can not be trusted and to seek alternatives (and for those attestation events).

3. There also isn't a need to whitelist keys. Confirmation of the profile can happen in any number of ways "out-of-band".