So it's basically an easily pluggable transforming HTTP proxy. That's pretty cool.
My question is, what does this have to do with Docker at all? I understand the use case, and I agree it's useful for Docker extensions. But this looks like it has no reason to limit itself to one application; this functionality is useful for a lot of usecases beyond Docker's API, and it could even benefit its design to be a generalist HTTP transform.
Also, this gives me echoes of xkcd [1]. Is the right way to solve the too many standards problem by wrapping it in one more standard?