@mikael Granted, I’m not an expert in Jasonette as I’ve only been lurking on the project, but looks like it supports user actions. IE: submitting form data when a user taps button, swipes, errors, etc. I don’t think I understand the the difference between jasonette and what your idea is (Its too early, still trying to wake up).
After re-reading, it sounds like you’re saying you want an app that consumes JSON (perhaps from REST API) and shows you the data in a way where you can build your own interface around it. Similar to pythonista’s UI builder but it would allow you to associate UI elements with keys/values from your JSON response.
Regardless, that would be a cool app!