Very neat! This matches up closely with what we have evolved for my group's legacy codebase to simplify handling AJAX requests. I suspect we're not alone in arriving at this sort of declarative abstraction.

Unfortunately, our implementation is rather scatter-brained and non-uniform. That's partly due to its gradual evolution and partly due to lack of free employee time to clean up bit-rot. I'm going to investigate this a bit more and mock out some examples for our product. I definitely think it'd help us organize our unruly mass of code. Good job!