Do you remember this quote, "There can be only one!"
Regardless, it is not the file system per se, but the controlling software; ASIMware's CDFS know to use the unit numbers of the SCSI ID numbers. You are aware that an A2091 (for example) uses ID #7 for the controller, leaving you 0 to 6 ID numbers for your device. Each device can have 7 unit numbers: a CDROM changers set to be device 3 will access each of its CD Drives by the unit numbers (0 to 7). There by each drive gets a number like 035 where the drive is unit 5 on device (ID#) 3.
You can do this by hand and set up a mountlist for each drive in a changer, or just use ASIM-CDfs that also allows each drive to be used with a GUI.
AS I recall, you can have up to 7 controllers or so, in your computer, in which case the mountlist might contain "235" for controller 2, ID 3, drive 5.