So once I moved all the motors to the botton and considered the complexity of delivering all those rotations to the joints, i really had to think twice about it. It just wasn't going to work. Too complex, too prone to failure.
So I simplified the whole thing immensely. Now it's just two degrees of freedom provided by two direct drive motors. A belt riding on the outside of the two planetary bearings / gear boxes will convey motion from the motor to the next joint. Two end stops located on the base will set the calibrations.
The robot will not be nearly as capable but it will be much more realistically build able by an amateur like me. Oh, and the actuator will probably be an electromagnet! Bzzzrp!