I haven’t looked into promenade so not sure on that.
if I’m understanding your question correctly with Frostr you can configure basic permissions on a given share within signing client (send / receive / both) meaning it has permission to either send a request to another share for sig, only receive requests, or both.
This effectively allows you to have a “third-party“ share (receive only) that you could give out to different clients/services for signing
nostr:npub1gg5uy8cpqx4u8wj9yvlpwm5ht757vudmrzn8y27lwunt5f2ytlusklulq3 I get this right?