....this is the same thing really. You can combine 3DGS functions to find the length of a bone, and then scale the model to fit before adding it to the physics system. Then you can create all your skeletons automatically.

The trick is to only create your skeleton of physics one you need them. Just animate the model as normal, then once you need them, call your function to create the skeleton, rotate it to match the current bones angles, then cancel your models animation function, and have it switch to a "matching the hinge angles" function. Then when your done with them, destroy the physics models, and have the bones do a blend into a "getting up" animation.