Another nice thing would be to be able to support multiple resolutions of a model.

They are doing that. At least DAZ and CL are, with low-res Jessi and James, and low-res M3 and V3.

IMO, they should consider different rigging for high-res and low-res models. Apparently, the lack of a buttocks group in the P6 figures was to make posing with IK easier. That seems like more of an animation issue, and perhaps better suited for the low-res versions of the figures.

It would make conforming clothing more difficult if the two versions were rigged differently, but if dynamic clothes catch on, that will be much less of a problem. I would expect animators, at least, to embrace dynamic clothing, so conforming clothing makers could perhaps stick to the high-res figures without leaving out too many users.