yea, i change the rig so that it wont move with the hips, but rather with the knee.
actually, u dont even need the kneectrl object. u can control the orientation of the knee with the knee attribute on the leg ctrl, its just there as a visual cue.

the average node is to keep the leg from flipping at extreme poses.

only thin with your pole vector constrain is that it moves around a lot. and it does not stay oriented with the knee, like my control ovject. and also translating in z or y seems to affect the orientation as well, i prefer only x to acffect orientation of knee.

but your rig is good. i guess it comes down to a matter of preference, if your are the one who will animate, then rig the way you feel comfortable.