Would it possible to "prep" a SCSI drive on a retro Mac for use in the A2000? By "prep" I mean format, load an OS image, etc.
Only if you write the software to do that yourself. So probably no.
Especially installing the OS really requires an Amiga emulator, even though it is possible to just copy the files over without using the installer.
Anyway, you would need software to extract the files from the ADFs and write them to your HD.
Heck, for that matter, could I just use an external SCSI drive (HDD, Zip, whatever) as a go-between from the old Mac to the A2000 to get access to more (downloaded) software?
If you install CrossMac on the Amiga, you should be able to read Mac formatted Zip disks.
