Everyone in Nostr already has a Schnorr key and the entire of Nostr works by signing and verifying with nsecs and npubs. So why would you mandate gpg to verify it? Just sign it with your Nostr identity and everyone can see it was you that wrote it. This is like saying "look at my new alternative energy car, of course in order to start it you need a jump start from an old internal combustion engined car"