you might try this one. first of all the reason for rigging the low-res polyObject instead of the subDVersion is all about performance issues. put the low res on a layer, put the subD-version of it onto another so you can turn visability on and of for both.

do not bind the subD to the skeleton. bind the low-res and use it like a lattice to influence the subD. in case you have a complete body, cut it into symetric pieces and bind them to the skeleton. to influence the subD with the lowPolyObject select 1 part of the lowPolyObject and shift-select the subD´s controlvertices wich are overlapped by the lowPolyObject, goto -> submenu Animation - Deform - Create Blendshape.

I think it is Create Blendshape, but am not 100% sure about cause I have no internet at home right now, so can´t prove it. but I hope you did get the idea of it. this way you can swap between low-res and subD any time. update time of smoothed versions is horror, so stick to lowest resolution geometry wich is bent to the joints.

cheers!