Excellent.  At first this seemed like a very difficult task but once I managed to wrap my head around how the Dynamic Data stuff is actually working the solution became pretty obvious.  The ability to add custom types to the DynamicDataFields templates is really pretty cool.

I do think that you should really consider native enum support similar to what I've done here.  It would be great if this was built in and didn't require a render hint.

Thanks.  Still really liking Dynamic Data!