Huh - that's actually pretty interesting and I hadn't thought of that as an option.. I know Preact was built as a faster alternative while being broadly compatible, but what you are describing is maybe even blending the technologies as that short circuit. neat.
> Stick to using JSX for the view
That's what I did. https://mutraction.dev/
My framework has approximately zero users and this is not a plug, but the idea is sound and it works.
I think LLMs, despite already being trained massively on React, can easily adapt their output to suit a new framework's-specific API surface with a simple adjustment to the prompt. Maybe include an abbreviated list of type/function signatures that are specific to your new framework and just tell the LLM to use JSX for the views?
What I think will definitely be a challenge for new library authors in the age of LLMs is state management. There are already tons of libraries that basically achieve the same thing but have vastly different APIs. In this case, new lib-authors may be forced to just write pluggable re-implementations of existing libraries just to enable LLMs to emit compilable/runnable code. Though I dont know of any state management library that dominates the web like React does with the view layer.