Did they release update ROM's when a new version came out? Or were you kind of stuck with what you had?
(I assume something of that era wasn't flash-able)
Usually an upgrade involved disabling the RM and installing the new software via floppies.
I found that out the hard way when installing a hard drive in one of these.
If you left the ROM enabled, not all for the OS would install, then it needed the Rom'd portions to boot (are weird problem).
I wonder if you could upgrade those ROMs?
And, for that matter, if a similar boot setup could be created on a more modern computer.