Even if you could
1. Install to the HDD
2. Start the game with the disc in the drive
3. Remove the disc and leave the game running
I think you could provide this function AND curb piracy at the same time. The only practical application would be to play LAN games. I'm sure there are 6 copies of Halo in every dorm room, and that might change if they added this feature, but I can't see it resulting in too many lost sales.