Hi Cameron, now I know why your name badge looked familiar at the last Innovation Day.
It would be a lot of work but you could make a small start - there's no reason why you have to use XAML, just need something creating the partial classes.
So, you could code up a DSL replacing XAML with something that was legal C# or go the whole hog and write a VS tool which generated C# the same way the XAML processor does. It depends on how much you want available to the code-behind file at compile-time.
Hmmm, with IronRuby, maybe a DSL in IronRuby
(DSL = Domain Specific Language for anyone reading who is acronymically challenged.)