Just one final thing regards my posts above. The system I describe requires collision detection, because in order for the figure to walk along a bumpy terrain, its feet need to collide with it.

The good news is that this could be achieved in Poser largely with technology it already has in place. All you would need to do is use Poser's Morph Brush to sculpt a terrain out of a subdivided plane object, then set it as a Kinematic Collision object so that the feet know they need to collide with it, therefore making the figure walk over it.