A very interesting idea. But it seems a little... fragile. Cables and cloth and everything. I expect it would be pretty high maintenance; you'd need to replace the tether and patch the balloon.
I like the idea of using them as emergency power sources in disaster areas. Portable, and a lot more efficient and clean than gas generators.
I wonder if you could rig one to a ship? (not a spaceship, an ocean liner). It would likely generate a lot of electricity in that form. Not sure if it would be enough to power the whole ship, but maybe as an emergency/auxiliary source.