I'm late to the party, but here is what I think:
- Hips/Legs
There are for more printed hips in the field than printed arms, so in my opinion to put complete assemblies of hips/legs into the library needs to be done, looking for them through the library might be extremely painful...
Also you always have a left and a right leg, they most probably have the same patter number, but it is easier to have the complete part there.
- Arms/Torsi
As with the hips, I think it would most make sense if there is a pattern on the arms. So we should have those combos in, at least. Other assemblies, with single colour arms, would have kind of a "logical" relarion to the main body, respectively it is just the job of adding an arm and giving it a colour.