Magnus can only develop high Cl at poor power-to-weight compared to a mass-equivalent power kite.
One way of visualizing the comparison would be to make a SS power kite of the same surface area and mass as the balloon fabric, with no flying motor-gen.
The math paints the same picture about power-to-weight. High Cl has traditionally only been essential for landing a large airplane on a shorter runway, when the plane is dropping and slowing anyway, bleeding off energy.
Let anyone do comparative testing for those who still have doubts.
There are many classic kite designs, “sticky” and soft, with multiple surfaces like a slatted flap wing; not the best flyers.