That's a good point. I've never written a client that is "multi-interface re-entrant" like that (I have used and enjoyed emacs-client). The nice thing about character cell terminals is that all the terminal handling falls out for free: I don't need to accommodate for anything (like tmux, or remote access (like ssh)), it Just Happens.

Worth considering (or modeling) how I'd write an emacs-client type of application though.