You could have a big tank with a piston inside to suck the gas out of the craft before unloading. Say the Japanese get to scale their nuke hydrogen one could be

You could have a big tank with a piston inside to suck the gas out of the craft before unloading. Say the Japanese get to scale their nuke hydrogen one could be transporting the stuff as cargo. You mention having to ventilate to get rid of leaking hydrogen. Perhaps it can go into the generators. While adding a layer of solar to strengthen the construction seems a good plan there is also fantastic wind up there. One might use turbines or even sails to propel the craft. If you make it truly large you won't need a gas. Can just use a hard vacuum... It's going to have to be big tho. At least a few km.