"Darrk" said ...Generally speaking, most "poly cruncher" tools give really bad topology. ZBrush's ZRemesher does a pretty good job, but even with that, to get good, animatable topology, you have to invest some time placing curve guides and polypainting to specify vertex density. That being said, getting a usable game-density animatable mesh from an existing high-poly model is a LOT less work than modeling from scratch.
Those are awesome. "Poly-cruncher" is included in most 3D Rendering software. It would probably be easier to poly-crunch their head/face and then put them on a pre-rigged model. Maybe one that's already skinned with similar features/clothing. You would probably want those high-poly models so you could render normal maps of their faces.