cross-reference with hundreds (if not thousands) of pre sampled 3d heads <<<

I am not a programmer, nor do I have any insight into how FaceGen works other than that as a user. But it's my understanding that the  "Mean Face" in FaceGen serves exactly that purpose. The mean face appears to be a neutral starting point that can accomodate various traits such as age and ethnicity.

I'm not sure how the new version will work, whether or not it will use a similar approach. Being that the link on the FaceGen site says that the integration will be easier, I'm really really excited about what might be coming!