Just a quick follow up. I tried this last night and had great results. All I needed to do was use the BootCamp utility. The same BootCamp drivers used for Windows 7 have enabled all the hardware features in Server 2008 r2. I did run into an issue where the installer for BootCamp wouldn't run for some reason. To bypass this, go into the WindowSupport folder, find the 'drivers' subfolder and run the application there suitable for your environment. That begins the same installation process as normal, so it's no big deal.
I have full use of the Retina Display and the Nvidia GPU seems to be working perfectly.
Also, I'm able to run Hyper-V server on this installation which means the EFI is enabling the Vt-x features of the CPU.
A+ Apple, well done.