Hi Ben,
I've forked your HTTP/2 package and implemented the HTTP/2 frame parsers along with some basic checks using draft14. While having Warp support it would definitely help, I'm actually planning on implementing a complete HTTP/2 proxy (HTTP/2 from clients, consolidated down to multiple HTTP/2 connections to backend app servers).
I would be nice if we can work together. Mighty is a web server based on Warp. Currently, Mighty implements reverse proxy only. I'm planning to implement (forward) proxy and supports HTTP/2 in forward/reverse proxy.
This type of work requires rather direct access to the entirety of the frame processing and stream handling aspects, while I'd imagine Warp would generally only expose a WAI interface.
I don't understand this problem yet due to the lack of experience. But if direct access is really necessary, you can propose to extend WAI. I think that web-devel@haskell.org is a proper place to discuss this. --Kazu