It would be huge, and has an obvious limitation of daytime only, unless a supplemental heat source is included.  Hot air instead of helium/hydrogen so no special tanking or materials required.  Side inlets also provide steering.  It would look boss.  I’m guessing it would be pretty slow.  Upside, unlimited operation as long as the sun shines and the fabric holds out.  Maybe a retractable insulated topside blanket to extend night utility.

Is there enough energy in sunlight to make this work?  What balloon shape would maximize solar exposure and minimize drag?  Would it be better just to have the turbine generate power for standard propellers?  Less cool, but better?  Probably need internal lens/mirror to regulate lift/propulsion sunlight distribution.

UPDATE:  I don’t know if this picture i’m about to post will show up, or if it will make any sense.  But Bryce requested it, so what the hey.

Okay, I don’t know how to point to a pic on Flickr to make it show up here.  Watch this space.

 Wow, lookit all those birds.  Is anyone else seeing this?  Hmm, I wonder what the total mass of bird up in the sky is right now that no one is paying the slightest attention to?  I bet they’d pay attention if it was the same mass all in one big bird.