They kind of sound like the Franks in d20 Future to me. But any way, based on what you have here I would say that a chimera could be represented by the covert Moreaus, as the covert Moreaus, at least according to the d20MRPG are supposed to still look human, but to be any real help I think the rest of us here will need more information, what sort of abilities do Chimeras based on different animals have, how much stronger or more agile are they compared to humans, are they as smart as humans, I hope I'm not just coming across as a jerk, but, these are all thinks that you'll need to consider.