I'm sure that going backwards to an earlier ROM would loose support for hardware, as well as any bug fixes to get the G3 to run. I've got another G3 now, and it's a Rage Pro Turbo and Rev. A good point would be to check Open Firmware versions here and from there I see that no other PPC has the exact same OF versions as a Rev 1 or 2 Beige G3. There are 3 rev.s of the ROMs, and I'm sure that they have special code to get the G3 and associated hardware setup to run an OS.
