I should have posted a video demonstrating the cat rig ages ago, but there were numerous issues with this rig, which I have now resolved. These included the cat caving in on itself when I rotated it, as well as numerous issues with the weighting, particularly in the cats chest in which it would go down too far if I moved the back control down. These are fixed and now the cat is ready to be animated properly. Here is a video of the cat rig, complete with controls, weighting, drivers and blend shapes. All of this was done by me, but I did get help with the weighting from James Tomkins.