It took me a while to figure out what you meant by Kazu's webserver package, since he's been hacking on Warp for a long time now, and using it for mighttpd2. TIL about http://hackage.haskell.org/package/webserver
I would say we should go for a WAI backend for ekg so it can be used by any
WAI-based application, including Yesod. I'll go so far as to say that this should be included in the 1.2 Yesod release (https://github.com/yesodweb/yesod/issues/475
Is the codebase stable enough that it would make sense to start hacking the WAI backend? Once it is, I'll email the Yesod mailing list and see if anyone wants to tackle this.
Also, a +1 for keeping `ekg` as a fully-functional package including a web server. If it uses Snap, Warp, or anything else, doesn't really matter to me, but I think it's the right approach to take.