It would be cool to see a Bluray Changer that does not cost $3500. I think it would be cool to write a text based OS that can organize the discs with a wireless keyboard to control. Since this would be ideal for a Home theater size is obviously not much of a problem.
An even further mod on this would be to integrate the PS3 And Xbox 360 into this design.
Possible Parts:
Sony VGP-XL1B2 Media Changer (also: VGP-XL1B)
Blu Ray Player
Additional Parts:
Xbox 360
PS3