If you were to remove the rails to retrofit something, just be aware that the Q7 requires you to remove the headliner to get access to the screws and that you'd have to something to seal the holes to prevent water leaking into the interior.

I do agree that both the Audi (Thule OEM'd) and Thule (Euro spec) cross bars are too short to be of any use for serious hauling. I can get my cargo box and 1-2 bikes up there, but no more. It's one reason why I invested in a hitch mount setup.