It would be awesome using the Wii interface. Perhaps triple the thickness of the Wii and allow for 5 disc's to be stored at once. Then each disc would appear as a seperate channel, and you could jus pick which game or movie you felt like playing at the time. It'd be great for quickly showing off a few games to mate's without having to pull each one out and put the other back. The cost would be quite massive, and disc stackers are generally fairly unreliable.
But this idea coupled with a HDD? I think we are onto something.