Do not assume that a non-USA product line up is going to be exactly configured as a USA line up. I didn't realize this myself until I popped into the web Apple Store after your comments.
EveryMac.com's listing of every manufactured and sold MacBook Air model with specifications
MacBook Airs are designed for light weight and portability as well as reasonable all around power in their class; they are not designed, nor meant to be graphic work stations, or processing work horses. As such, the graphics on Macbook Airs are built onto the logic board and soldered onto them at the factory. Nor were "upgrades" installable at the store as you claim. . . memory in a MacBook Air is soldered to the logic board, as are the graphic chips. The only upgradeable component in a MacBook Air is the harddrive.
Had you said it was a MacBook Pro, your claims would be more believable. The installed Intel i7 is still not "detuned," but will be clocked down when operating on battery power. Plug it in and it operates at full clocked speed. And, again, multiple PC Magazines rated the Mac notebooks as the best Windows machine in multiple articles. So all you had to do was install an OEM version of your favorite install of Microsoft's OS in Boot Camp and you would have been good to go. Doing so by-passes any "de-tuning" or OSX issues you claim as it boots as a Windows computer.
I have a macbook air 11 which met my needs being small and lightweight, but I would obviously prefer a retina display and will jump on the 12 inch air with retina when it comes out early next year (maybe Christmas but I think next year is a better bet).