1) It's not possible from a cryptographic point of view; 2) We don't have any official solution, only some proposal to invalidate and promote a new key pair; one solution by nostr:npub1l2vyh47mk2p0qlsku7hg0vn29faehy9hy34ygaclpn66ukqp3afqutajft uses a secondary key, similari to what you envisioned, to signal (via clients automation) the burned key and to autofollow the new one. It's an important issue and I agree it's critical to address it for mass adoption. I think we will use bunkers, probably multi signature (so mainly custodial, but with a good overall security) and key rotation will be used only for exceptional events.