@**Cage**,

I think it presently works like this. The xrot in the jaw is slaved directly to MouthOpen in the head, this is just a controll channel with no deltas. JCM-MouthOpen in the head is the actual morph to open the mouth, and this is slaved to a valueParm in the BODY, "JCM-MouthOpen", which in turn is slaved to xrot in the jaw. The "ValueParm JCM-MouthOpen" also drives other JCM-MouthOpen channels in various actors.

To my mind the simplest solution is probably to change the valueParm in the BODY so it is slaved to MouthOpen in the head. The attached file does just that. It assumes that no slaving code has been added to the "ValueParm JCM-MouthOpen" in the BODY, other than what odf put in there originally.

With this new set up, the MouthOpen dial drives the jaw rotation, and "ValueParm JCM-MouthOpen" in the BODY, and the valueParm  still drives all the other associated JCM-MouthOpen channels in other body parts the same as it did before. You can then use multiple mouth opening morphs in without conflict with odf's MouthOpen, and if desired in conjunction with expressing that morph. Rotating the jaw directly from the jaw actor will have no effect on the head, and if you want to express MouthOpen without driving the jaw rotation, you can use the "ValueParm JCM-MouthOpen" dial in the Body.

All this does a certain violence to odf's origlal concept, and I don't know how he will feel about it, but if you don't tell him we did it, neither will I.

The above does not actually give you a dial to turn the slaving off/on, but I think it gives you the flexibility to use other morphs that open the mouth, or io xrot the jaw without the mouth opening. I will think about how to add a dial to turn the slaving off, whilst still maintaining the ability to rotate the jaw and use the MouthOpen morph. I'll get back to you on that.

P.S.
I wrote this in responce to your original question, before reading the subsequent posts, and have not had time to digest them yet.