For now I have the version below. If you look carefully you can see in the un-smoothed view there is still some glitching, however when smoothed it tightens into place.
This skeleton may be revisited, but for the meantime I am quite pleased with the general skirt movement. However it will be the rigged version of the character, when I can animate her personality, that will truly show any skinning and skeletal issues.
The first issue I have spotted is that parenting in foot controls accidentally detached the foot joints from the main rig. When the joints were parented back in, the mesh no longer behaved as expected. So I simply grouped things back into place. The video below shows the current skirt behavior with the grouped floating joints.