Re prior art, there are some solutions like this in the Clojure world, given the data-centricity of the language.

See Hyperfiddle:

http://www.hyperfiddle.net/

And also Vase:

https://github.com/cognitect-labs/vase

This is also similar to API mocking services.

Agree with other comments, it is important to find a customer.

Good luck!