Yeah, I plan to model a skin for him, and bind it to the rig. Then set the muscles to act as influence objects. So the skeleton is parented to the rig, the muscles are attached with clusters and latices to the bones, and the skin is bound. That way the rig drives the skeleton, and the skeleton drives the muscles, the skin is bound to the rig, and is intern driven by the muscles. Kind of complicated, but it should give some awesome results.