Performance of a PPC core on a low end FPGA would be poor and a waste of resources when you can easily buy a more powerful PPC instead of spending money on an FPGA. Also the Apollo team have no interest in PPC or any RISC architecture. RISC CPUs were conceived to simplify the development of new CPUs with higher clock rates compensating for the relative lack of performance compared to similarly clocked CISC processors. At that time the tools for design CPUs were very limited and the costs were very high. So Motorola thought it made sense to join a partnership to develop a RISC architecture to go up against x86 instead of trying to push there 680x0 chips to higher complexity and speeds. RISC lost the desktop computer war and PPC missed out on the "CPU/MCU/SoC of things" to ARM. The Apollo team like the 680x0 architecture and are fully focused on developing the Apollo core and accelerators/sytems based on that core so there is no chance of them ever doing a PPC core "Vampire".
