Welcome to Chestnut! Thanks a lot for wanting to contribute!
I think having an example of how to do client-server communication would be useful and great to have. The main reason it's not there is that there's no real consensus in the Clojure world of how to do it. REST? Something with event sourcing? Replikativ? Datalog? That said I think Transit as a format and a traditional REST-ish API are still good defaults to start from. I'm not sure if it should be behind a feature flag or not, but I'm leaning towards putting it behind a flag. Maybe
Do you have an example project that people can look at? If not I would suggest to start there, generate a Chestnut app and start making the changes you want to bring in. That's easier than immediately trying to weave it into the template, it gives you an opportunity to experiment with the approach you want to take, and it's also an easier way for people to look at it and give feedback. In the end you take a diff and you see exactly what to add to Chestnut.
Which middleware and which ajax lib were you thinking of using? I personally have good experience with ring-middleware-format and cljs-ajax. I like ring-middleware-format because it does HTTP content negotiation, so it'll serve transit if a client asks for it, or JSON or something else. cljs-ajax also defaults to transit so that tends to work out of the box.