So then it wouldn't be that hard to setup aix or ppc linux emulation in
   netbsd/powerpc?  or would this not work because netbsd/powerpc is a.out
   (thats what the gcc patch setups anyways..), and ppc-linux is elf.  And
   vice versa (if the linux server supports a.out)?

the execution layer is separate from the emulation layer.  theoretically,
one only need include support for a particular execution format in their
kernel (and soon hopefully these will also work as LKMs).