altering the profile in combination with tread width but keeping within a reasonable percentage of the OE rolling radius is in theory fine
In combination with a reduced ride height it may indeed give you the look you are after.
Be wary though moving away from 'known' combos (17's 45profile , 18's 40profile , 19's 35profile)
may give you ride/wear and handling issues you wouldnt expect. Rim protection will also be reduced.
If you want to do it fine, go for it
Personally I would be looking at others ways to enhance your car but sometimes its good to be different......
One of the GTI's facets is great agility/handling which you dont want to spoil , but you never know it may improve to your liking
note that jonnyc is moving away from std sizes to fit certain rims and tyres