I agree. My proposals then would be:
- switch to RSA or allow external utilities like GPG generate and verify message signatures;
- relax the transport requirements (websockets => normal TCP sockets, HTTP POST, scp, rsync etc), ideally by storing the notes as (signed) plain text files on the relay;
- allow to substitute JSON with a Recutil-like or MIME-like format that would preserve the plaintext but let us specify some metadata.
Hold on, I think I have seen all this somewhere already... It probably starts with "e" and ends with "mail".