>Behavior customizability should come from tweaking the auto generated json config, and adding some HTML and JavaScript to higher order components.
Show me a single component on any platform which can be customized via properties to "do everything".
Show me a single component on any platform which can be customized via properties to "do everything".
There have been countless attempts (http://thedailywtf.com/articles/The-Mythical-Business-Layer , http://thedailywtf.com/articles/the-inner-json-effect , http://thedailywtf.com/articles/The_Enterprise_Rules_Engine to name but a few) at trying to reimplement a fully-fledged programming language in XML / XSLT, JSON or whatnot. Ultimately, all of these attempts seem to end up being more complex and unwieldy than the tools they were intended to replace.
The OP calls for a tool that allows you to automate most of the cumbersome work involved in building web UIs. Perhaps programming languages just are the closest abstraction that still allows for a sufficiently large degree of freedom when it comes to accommodating specific requirements.
After all modern programming languages and frameworks already automate most of that really arduous work. They allow us to define data-driven applications in concise terms that for the most part already resemble a specification written in natural language.
More accessible languages that more readily provide clear feedback (think of Bret Victor's work for example) could be a way forward.