That’s awesome!
That’s less awesome (but understandable) 
It could just be my misunderstanding though. I’ve only ever seen the JSON config as something that’s modified via a REST interface, if you can similarly modify a JSON file and provide that just like the Caddyfile, that’s all good too. I realize it’s not difficult to use the API for JSON, I’ve got Insomnia setup with snippets for easily doing so, but I do find Caddyfile nice and quick for learning/experimenting.
Does Caddy export OpenAPI v3 or similar for making adoption with tools like Insomnia even easier? Currently I have to look up the docs and create/type out what I want to try. I remember it not always being entirely clear and having to guess a few attempts until I got the outcome I was expecting.
If OpenAPI v3 is supported, you could also get nice doc generation with ReDoc, see an example here.