By using a four-bar linkage to replace a knee joint it may be possible to eliminate spinning disks at the knee joints!  The number of breaks would stay the same. The two from the knees would just move up to the previous (hip) joint.  This will increase the efficiency because the number of spinning gears and disks will decrease.  Allow disks to spin at higher speeds.  Reduce weight and make limbs lighter by moving the breaks closer to the body.  Reduce the bulk of the robot.  A bipedal configuration will require only 6 spinning disks.  This will however put a higher thermal load on the hip joint disks.  Also it will reduce the angles by which the joints can turn.  This change however leads to a flat hip frame which will be easier to print.  And here are my Hand Aided Design (HAD) drawings:

In this sketch brakes would be mounted on A and B.  Shafts and how A sits on the shaft are not shown on the left.  Disks are not drawn to scale on the left and omitted completely on the right.