yeah, i think add a field to nip-11 info that gives a codec name
the other thing to be attended to is the websocket negotiation, possibly a new field in the header would be useful such as a mimetype, if it's upgrade and json, then json, if it's upgrade and cbor, it's cbor, etc
i think better we don't tamper with the API though - retain the envelopes, just in a different encoding
i also have been saying for some time it would be useful to add a negation operator to filters so a client can request to not see events from authors or events it already has... a lot of what negentropy does is working around this problem also
and maybe a new variant of req that only returns event ids instead of whole events
anyway, now i'm going off on tangents