|PegasOS II? --|
Why not make a motherboard that will be compatible with the CPU upgrade modules for the Mac computers?
http://www.gigadesigns.com/ is one company that makes boards that can be used within AGP Graphics (Sawtooth), Server, Gigabit Ethernet, Digital Audio, Quicksilver, and Quicksilver 2002 motherboards. G4 CPU modules they make are from 800Mhz to 1.4Ghz in speed.
http://www.sonnettech.com/ is another company their G4 is in the same 800Mhz to 1.4Ghz range.
The other plus is that we could use someone's lower speed G4 (say a 500Mhz) for cheap off of Ebay.
I'd gladly buy a PegasOSII board for $100-150 and use a G4 500Mhz from Ebay for a while.