One massive problem with this concept is the decreasing availability of helium. Disney recently had to make massive cutbacks to their helium balloons because of decreasing supplies of helium and skyrocketing costs.

Crazy as the idea of the hybrid airship sounds, yes, it could potentially be a workable technology. But lack of helium would be a dealbreaker.

Here's one link. You can find more online:

http://www.independent.co.uk/news/science/a-ballooning-problem-the-great-helium-shortage-8439108.html