This is kind of turning into a random ideas topic.
Here is another one: If you have a rotary AWES where you are using ground control by varying tether length, a good way to do this I think is by adding (multiple, concentric) cylindrical cams that can rotate (to be able to control the direction) and that can move in and out (to vary the amplitude of control line variations).
The cams would extend from the nacelle and go around the shaft. They would only come in contact with the control lines. They would look like concentric tubes, with the end that comes into contact with the control line being shaped.
Maybe you’d use a number of these cams, concentric around each other, to even out the wave of control line length you would be producing. If you imagine the graph the control line length would make if you only extended the cam out partway so that it didn’t impact the control line through part of the rotation, it would be a flat line during that part of the rotation instead of following the profile of the cam.
Another reason to add more cams might be to add more control inputs. One could maintain elevation angle and heading while others could do different things.
IIRC @someAWE_cb uses mostly the same basic principle, and I am sure the same basic principle is used in many other applications.
The benefit would be that you don’t have (strong) motors or other actuators constantly varying the tether length around the rotation, one for each tether. There are probably many drawbacks as well, one would be that you can probably only design a cam, and determine if it’s a viable solution, after you’ve tested your control inputs in some other way.
A different question might be if you can do ground control at all if you are doing torque transfer. I think a relevant question for that is the phase difference between the top and bottom rotor. The smaller the better I think so that your control input results in most of the kites in a train being pointed in mostly the same direction and your control input and added drag from that not being mostly wasted.