let me explain, the reason we use IK is because its easy to position the controls but it moves in strait line and the reason we use FK because it makes nice rotational transition between frames or makes arc while moving.
so i was thinking of using an "Aim Constrain". what i mean with this that we make the regular joints then when adding controls, make the cube cc (control curve) at the knee an make an aim constrain between the cube cc and the hip joint.
so if u want to lift the knee u just click on the cube cc then position it then if u made some keyframe and animate and then to see better let the knee joint make a motion curve then play u will find a nice arc done this way, also to control any joint make the cc on the next joint and aim constrain it.
i didn't figure out a good way of parenting and making the hierarchy yet, but that's not the issue i want to know if its really efficient or worth trying or it was a bad idea and i should stick with the regular IK FK controls, so give me ur opinion.
That's an image with aim constrain.
and that's another image after number of frames.