Sorry, expiration dates yes, but not arbitrary revocation.

Anyway, none of these delegation schemes works without some giant bloat or clients and relays and/or a lot of state required for the most basic tasks. Maybe it's a good idea to make the entire protocol a magnitude more complex so we can offer that kind of stuff, but for now I'm firmly in the camp of it-isn't-worth-it and nsecbunker-is-probably-enough, but also most-people-will-use-custodial-keys-anyway and that's-fine-because-most-people's-keys-aren't-really-super-important-and-can-be-rotated-manually.