Why not make a nip where you can authorize a different nsec to post on your behalf. So I could make a second nsec and using my first I publish a message that lets everyone know to treat the associated npub as me. Then I could give that nsec to a server or use it in an app I don't trust, and if they use it maliciously or I don't want to use their service anymore, I can publish an message saying that npub no longer is valid for my account.