#[2] #[3] #[4] would be useful if users could cross sign keys and rotate them. Relays could identify the signatures and transfer ownership of profiles. The ability to revoke keys -think gpg/pgp- if compromised is needed. There's no tech support for lost "passwords" and identities stolen. This could be made almost transparent and seamless for normies.
Discussion
I was thinking a bit about this a while back. Problem is it needs to be transparent for even grandma. People forget passwords, lose revocation certificates and private keys. Maybe a short pin that is occasionally asked from a user like Signal does?
#[3]
NIP-26 could be useful here and NIP-06 for the root/seed key and phrase.