At some point in future you will probably also want to get the 3.1 ROMs, so you can run the more recent OS versions.
I also think you should definitely work on getting a complete set of WB disks. I don't think your method to date will yield satisfying results.
If you particularly want to run an older OS, you can also run kick switchers, or softkickers, to give you access to an older kickrom set on demand.
Did you buy the A2000 with a bunch of floppy disks (I must have hundreds)? When I bought mine, I was also missing some of the original install disks, but there were badly labled backup copies within the pile of floppies, so I use some original disks and some backups when installing the OS. You may possibly have a similar situation.
