I scored a cheap 7-disc changer at university surplus, specifically for that game. It was only a 2x drive behind the changer, and I needed to source a SCSI controller card and cable, but I got it all going and suddenly I had LUNs galore!
The game was kind enough to let you specify different drives for the discs rather than assuming a single swapping situation, though it would check them all at launch time, which was quite a slow affair. But once it was going, it was great; as you moved between regions in the game, the drive would simply change discs and spin up the new one and away you went.
ISTR they did a certain amount of duplication, some overlap between regions would be on both discs, so it wouldn't require swapping constantly if you were right on a border. But at some points it would flip back and forth, and the changer made all the difference.
I think you're right that some of the data was duplicated. I can't remember if any other multi-cd games allowed assigning different drive letters to different discs. Also works with DOSbox
D: disc1, E: disc2, F: disc3, G: disc4, H:empty I:empty: J:empty.
The game was kind enough to let you specify different drives for the discs rather than assuming a single swapping situation, though it would check them all at launch time, which was quite a slow affair. But once it was going, it was great; as you moved between regions in the game, the drive would simply change discs and spin up the new one and away you went.
ISTR they did a certain amount of duplication, some overlap between regions would be on both discs, so it wouldn't require swapping constantly if you were right on a border. But at some points it would flip back and forth, and the changer made all the difference.