Why don'tyou have a go at hacking it to work on a peg? If you get the source for the x86 DMA beos driver and port that to PPC, then that would take care of some of the southbridge stuff I think. That would be a start.
Because I don't own a copy of BeOS r5 Pro, becuase I don't have the better part of a grand to get a full settup, my missus would kill me if I spent that much on a theory.
Also I'm working on porting XChat to BeOS atm which is just a case of recompiling gtk2 for use under BeOS and then running the makefile. Programming isn't my forte (being dyslexic can be a pain at times, like learning languages).