I had wondered how the line could turn the cylindrical balloon without deviating and going out.
As for the prototype, we can clearly see the fixed bar which carries the guides and which makes it possible to restrict the trajectory of the line around the balloon.
But for the rendering and a video, it seems that there is a shell carrying the guides and located around the balloon, but fixed. There should be bearings to allow the balloon to rotate, and the hull prevents the line from coming out and deflecting.
So a fixed element is required. The same would apply to all possible variants, whether in yo-yo mode with winches as currently or here, or in rope drive mode as here or there.
This leads me to think that if we can rotate the balloon around said fixed shell with a line, we can also use this same shell (then rotating while the balloon would be fixed) to rotate blades around a balloon or a round kite like here. The question would be whether putting a large annular generator, which would perhaps be lighter, would really be advantageous and reliable. Nothing is certain.