Another thing that just popped up in my mind just now: I think the Turks would've gained a lot more under this what-if if the Turks settled for allowing the passage of German troops through their territory and hold themselves to very limited defensive action. I think this would be more feasible for them because the Germans would bear more of the fighting. I doubt, though, if the Germans would settle for such an arrangement. Hitler would undoubtedly demand more from Turkey.