Or actually just incorporate pgp as the "multi sig." A pgp signed message posted to the original npub proving the new npub.
Discussion
A pgp-signed "revoke npub⁰ and replace with npub¹."
Maybe pgp should even be the/a new verification standard.
nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z nostr:npub1jlrs53pkdfjnts29kveljul2sm0actt6n8dxrrzqcersttvcuv3qdjynqn