How is this going to help when admins aren't looking into hacked accounts? Many people have signed messages from addresses that are still visible, but they're just not being restored and theymos' auto-system likely isn't going to help that either as I doubt it will take into consideration deleted posts, but even if it does what if somebody has another or an older address posted. Can they still claim the account back?
I hope it won't be based on a post but rather set in account profile without the option to update or remove it (except perhaps using a signed message from the old address although that opens some loopholes). At least that's how I'd do it. I'm not theymos in case you're wondering.