Quote - Your problem afterwards would be rigging the new model for facial expressions and animation.  But the texturing will take considerable time pending if your UV mapping is spread out correctly.  Adding photo crops for specific facial areas is basically cut and paste with resizing and filling in with skin coloring.  The real challenge is creating the bump maps for dermal pores, wrinkles and scars. 

Yeah, luckily for me, my wife is a Filipina, who is 38 but looks likes she's in her 20's. Hardly any wrinkles, and no scars at all. It will be the pores that have given me a challenge. I asked her to take some good close up shots so I can use them. She is excited, but I told her not to hold her breath. It's going to take while.

Is it possible to use the new head on say, Sydney's body, and just apply the rigging? I know you can replace her head as a prop, but that doesn't include the rigging.

Maybe I will just create the whole body and rig it later...

If I had a nickle for ever time a woman told me to get lost, I could buy Manhattan.