The GTD Blueline comes with 17's as standard - other than that its a normal GTD.
Therefore, 17's go on just fine...
As others have said, in Germany a GTI comes with hardly anything, including 17's as standard. Mind you, it does only cost something like 14000 euros or something.
Was bored and went on the Konfigurator at volkwagen.de.
So a GTI 3dr DSG facelift in metallic paint is 32500 Euros. That's with 17" wheels, no AID, no App Connect and an old style basic nav screen (not the new glass one thats std here as thats another 1400 euros!).
So basically we are getting a pretty good deal here!