- I had an idea that might let you easily change proportions of the rig without having to do the whole Rigify-style script.
If you divide it out into two separate armatures - a control rig with all the IK chains and other constraints, and then a controlled rig with just the deform bones, you could then change the proportions of the deformed bones more easily and without accidentally messing up the control rig, since it’s a separate object.
Here’s a file where I’ve done this - basically just two copies of your armature, pointed the constraints from one at the other, then deleted the unneeded parts from each.
It would probably be pretty trivial to script adding the constraints, also.