Oooooohhhh ❤️❤️❤️❤️
The delegate key thing (NIP46) as to happen of course and delegation with expiry like X509 certificates. Expiry means implicit revocation.
Keeping an eye too on those ESP32 devices and their security properties, like flash RAM encryption etc. I think there have been security holes there in the past. They would make for great "open source Yubikeys" with their broad availability.
In case what can also use a see dedicated crypto chip normally like ATECC608B or NXP SE050 but those don't normally do secp256k1 because that shit it exotic as fuck and is really hurting nostr.