I think it would be cool if they made the Helios more like a derigible where it could use uncompressed (or relatively uncompressed hydrogen) in their fuel cells so that it could aid in the aircraft's lift and use also use the hydrogen as fuel and thereby cause the propellers to need less propulsion at least part of the time. Instead of loading the wings full of fuel causing it to be heavy during the first half of flight, it would be just the opposite, the hydrogen fueld would cause it to be light during the first half of flight. However, after the airplane used up the hydrogen fuel it would drop like a rock. I suppose the size of the craft would have to be huge to carry that much uncompressed hydrogen. It would be an engineering marvel to have an aircraft that could shrink and become smaller and less derigible shaped and more airplane wing airfoil shaped during the flight to keep lift efficiency as high as possible.