I've had a lot of great success with this project. I've done so much trial and testing to see what still works, what's available, and what can be made to work.
The greatest new endeavor is one suggested by
@barracuda156 which seems to add RAW compatibility to older 'NIX systems. The extension or whatever it's called (I still have not wrapped my head around Macports since there is not a single instructional guide or even a useful description of it) is Libopenraw.
The bigger news is...now there's two of them.
For about $30 more than I paid for my 4,1, along came a local 5,1
with Westmere CPU's. Now it's
only 8-cores but at least I can finally test Leopard on the architecture.
As expected from several in this thread, Leopard begins to load kexts and halts. In Verbose mode the kext loading meter bar made of period symbols gets about 70% through then halts and never proceeds.
I've burned up some good brain cells trying to find a modified kext that doesn't check CPU but assumes CPU so it can load power managers etc. I wouldn't know what CPU to spoof that would be appropriate for Westmere either so one hurdle after another...
For the time being, there are two of them.