Maybe you are to far in your process, but what if you set the thigh joints like real thigh joints?
A real thigh bone is shaped like an L attached to the pelvis bone.
How would it work if you align your thigh joints like That L too, and making the longer bone a stiff child of the shorter bone? 
That means a Y rotation of the thigh parent bone makes the leg bend,
a Z rotation of the thigh parent bone makes the leg move to the side,
a X rotation of the thigh parent bone makes the leg twist.
Just an idea, that someone might be curious to explore.