E-mail is an already archaic technology. What about people that used disposable e-mails? (It turns out that cryptoenthusiasts are also fanatics of never disclosing personal data to anyone).

Perhaps using a signed message from another key could be used (a configurable bitcoin wallet, perhaps?)

To change (whatever), please sign this message with (BTC address; that should also require a signed message to be changed):

"Change the data of my account: TIMESTAMP"