Considered doing it by extending NIP-46? We are working on doing a remote signer for Bitcoin in relation with Angor in this manner: https://github.com/nostr-protocol/nips/blob/master/46.md
I also have a new NUT for cashu that needs more reviews and eyes on it.
https://github.com/cashubtc/nuts/pull/250
This is an implementation of a signer that stores the keys on the secret service of linux and communicates through abstract sockets:
Considered doing it by extending NIP-46? We are working on doing a remote signer for Bitcoin in relation with Angor in this manner: https://github.com/nostr-protocol/nips/blob/master/46.md