Yes, I know, not for the first time.
You said this project could be done in 2 months if you didn't do the front-end. That seems to me to imply that you want the front-end done using in-house expertise. IIRC, you're very fond of proven technology and don't like being a guinea pig.
With all of that, why not use something well understood like plain-old VB or plain-old Delphi or plain-old whatever your Windows UI developers are happy with? Being on the bleeding edge (with .NET or especially Mono) seems very unlike my picture of you.
Confusedly,
Scott.