Hi Mat,
I did find a somewhat “ugly” workaround by heavy use of stacked “Layerblend per bones”-nodes.
In each blend I manually added branch filters so so that the lower body is completely driven by control-rig, whilst arms are driven by one set of animations and torso drven by another.
Not really happy with the solution as It feels that I’m working against the tools rather than with them, but maybe it could help you.