If you want the attestation to be technically meaningful here are few things that have to happen (and that do happen on Farcaster and elsewhere):
Everyone who followed your old key before timestamp x (time of theft) now follows your new key, automatic.
DMs sent to your old key can be read using your new key (and no longer read using your old key)
Posts from your old key show with your new avatar and handle to anyone browsing.
And 50 other things.
How are these things to happen Nostr? If what you’re suggesting is just a nostr-native alternative to an adding your NIP05 to your new key then we already know what a non-solution that is. And if you want those things above to happen then you don't need a blockchain per se but you need a hard fork.
