I sincerely doubt that the UCD was originally designed as a "balanced" rudder. More like 'It looked about right, and should sell a bunch'. If it had been designed correctly in the first place, do you think there would have been all of the cross coupling?
I fail to see how a closed loop has more torque than a single push rod . A closed loop may take some of the backlash out of the system. I think that you will find that torque is force*distance, unless you reduce the distance that the rudder is moving the torque will be the same. Just my 2 cents worth.