The ODD is 9.5mm, the HDD bay is 12.5mm, so it's not like the SuperDrive has anything to do with thickness.
Lol. The reason why they can't put Blu-ray onto a MacBook Pro is not because of iTunes but because there is NO SLOT LOADING 9.5mm BLU-RAY DRIVE in existence.
Please, lose the misconception that adding Blu-ray will hurt iTunes movie sales. It won't be as severe as you might expect, and iTunes mainly runs on music and apps, not movies.