My recommendation is to work with the oskit instead of with gnumach. The oskit has good support for using gdb over a serial port, which I would think ought to work fine with some sort of virtual serial port plex86 has. If you can get some oskit example kernels to work, and use gdb on them, then we can start on oskit-mach. And if you get that far with plex86, then I will eagerly start using plex86 myself.