Unless I'm misunderstanding your question, it seems you're overthinking this. You tell Poser which map to look for the texture for each part - like V2Head.jpg and V2Body.jpg (or GizmoLeft.jpg, GizmoRight.jpg and GizmoTop.jpg). If you switch the file names, parts of the body texture will be mapped to the head, and parts of the head texture mapped to the body. You'll end up with a patchwork because the images on each map haven't been drawn to fit the appropriate body part.