I have read on some forums that its possible to flash the firmware of some Mac Superdrives with custom firmware, that way regions can be changed an unlimited amount of times. Its extreamly risky and could render your Superdrive completly useless.
Another potencial solution would be to get a cheap external DVD drive and connect it to your Mac
One thing that alot of people do is boot into Windows XP / Windows Vista by using BootCamp and as you know under Windows you can play an region with some software..
Good Luck