Earlier quoted context omitted.
I agree, Nancy is a lot of fun to use with Mono. However, I've been stuck trying to get a WCF (older ASP.NET) application running on Mono for a while now, and it's been a huge pain.
Forget about older ASP.NET and WCF on mono. The core of ASP.NET (System.Web assembly) doesn't feature in next version of ASP.NET. WCF hasn't seen any effective development in years. The new stuff (ASP.NET vnext) will be highly mono compatible and like the current OWIN stuff, entirely decoupled from IIS.
Should be a fun week!