There is another way that I was playing with a while back, and will do again eventually.
It cant hold a candle to valves effects, and there are still significant limitations,
but I was only at an EARLY stage of development when I put it on hold.
(No performace testing or its like have been performed either. So if anyone can see
any significant factors I havent taken into account, I would like to hear them.)

Most importantly, it fits your requirements. ie Single-mesh models, with bones.

Just follow these steps in your head, and if anyone wants to ask any questions for clarification
or on the reasoning behind any step, just ask.


1: Identify the bone whose HINGE will be the severing point. We will call it "CHOP".
2: Duplicate whole model, including skins and bone-positioning and origin-point.
3: On the ORIGINAL, re-scale the CHOP bone (and all its children) down to 0.001.
4: On the DUPLICATE, re-scale all the bones EXCEPT the CHOP bone(and its children) down to 0.001.
5: Create two "meat ball" entities, and scale them to match the "stumps" of each model.
6: Attach one meat-ball to each entity's "stump".
7: Make sure the duplicate (and its meat-ball) is PASSABLE relative to the original model.
8: Apply physics to the duplicate, and add any sound/visual effects required.