Yeah, weight maps.  Preferably weight maps that double as soft body maps.  Some of the above things have been addressed already.  I think the 3 level search will make library management easier, or less important.  I'm not sure about the subdivision thing though, but I thought the displacement mapping+smoothing was how people used Poser with zBrush.  Not sure about improving the poly response (preview or render?) as the previews work well on my athlon 1900+, and the improvements to rendering time have been mentioned already.  So, yeah, better joints/rigging is my top choice.