I think it’s pretty clear that disenfranchising either key (withdrawal cred or validator key) is not a great idea, so perhaps this scheme isn’t worth exploring as a way to handle withdrawal cred loss.
However, a modification of this proposal where signatures from both the withdrawal credential key and validator key are required for rotation would allow us to update withdrawal creds for other reasons (i.e. the existence of new, more fully featured prefixes).
I strongly feel that the option to ‘upgrade’ withdrawal creds should exist and a new canonical ‘WithdrawalCredentialsRotation’ contract seems like a clean way to do it.