OTOH that's an interesting thought and it feels like just an addition of one command to whatever there are in actions ( https://twinspark.js.org/api/ts-action/ ) right now... I need to think about it a bit. :)
— Require additional client-side templates and then it's back straight to hell;
— Require really specific JSON structure, basically HTML-in-JSON, which will be ugly as hell and totally meaningless. Meaningless, because then it means I need to adapt my API to this format, and then I can just make it return HTML.
As for the first - it could give a way to use legacy apis and static data. Not sure if I want this in the core, but… how hard can it be?