Personally, I would put a scalexyz controller on your scale, then have a seperate float expression on the x y and z channels. Then say the X is the length of your bone, have a expression on there that factors in your distances in order give you lengthening/shortening. Then also have the fatness of the squash and stretch…
I don't really have a solution to your entire problem, I do have this script that constrains POS/ROT/SCALE all at once. DOWNLOAD 1. Drag and drop it into the 3ds Max viewport to install. 2. Open Customize User Interface, and look in the "monsterBlues" category to bind to a hotkey or menu item. Usage: select the slave…