cider-connection-message-fn is not used on 1.3 I think. Maybe it should be the default value for cider-connected-hook

https://github.com/clojure-emacs/cider/issues/3172

Seems unlikely that someone will spontaneously volunteer - even more basic things like getting a cljs repl flawlessly for various use cases still need some love But any PR in this direction will certainly be reviewed and we'll help with whatever is at hand for getting it in :)