A reasonably high poly version would be very pleasing to me.

I know it's been said that very few renders show an open mouth.  But I think that's a good reason to pay attention to the inside of the mouth.  So few renders of V4 show an open mouth because her teeth look like chiclets.  Poor girl can have a beautifully realistic skin but the moment she smiles, she's a toon.  No wonder so few people render her smiling.

Also, if your figure is going to be used in the erotic market, I'm just guessing that the mouth and lips might get a fair amount of attention.  I could be wrong, but hey.

I really like the idea mentioned above of a very low res proxy for dynamic calculations.

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PoserPro 2014, PS CS5.5 Ext, Nikon D300. Win 8, i7-4770 @ 3.4 GHz, AMD Radeon 8570, 12 GB RAM.