Why not keep a history locally? You could do the prompting or not -- but even then instead of overwriting you still keep the previous versions.
I do like that Gossip keeps a local copy and only overwrites -- or merges upon an explicit button click: 
Discussion
Someone should also just host a metadata archiver relay that stores all versions of everybody's metadata (by just querying other relays) and then offer a metadata recovery service. Maybe #[0] from https://erdaltoprak.github.io/nostrid/.
I imagine that losing follows and whatnot won't be an issue for people that only use one client, right? And then once you're using multiple clients you should also be open to using a dedicated client just for managing your contacts and so on.
#[9] already keeps metadata history and allows to check it on https://nostr.band .
Maybe it could add also the Contact Lists?