Right this makes sense, I wonder if it would then be a good idea to abstract html to JSON, making it impossible to include css and js into it
If you play with A2UIs generator that's effectively what it does, just layer of abstraction or two above what you're describing.
Curious to learn more what you are thinking?
One challenge is you do likely want JS to process/capture the data - for example, taking the data from a form and turning it into json to send back to the agent