Rigid, lightweight and scalable. It's a tall order. yes, well, get there, eventually, but for now I think that hydrogen with good safety procedures is the most cost effective option by far. We can make the stuff out of sunlight and sea water! (With some help from photovoltaics.)
We don't need perfect containment, since it's nearly harmless when it leaks. And it will leak. Much like a vacuum, total containment is difficult to achieve.
So, rather than wait fifty to three hundred years to work it out, we can have cheap heavy lifting devices up in a year or two, that can work almost anywhere in the world.
The big problems with airships to my way of thinking are:
1. Public perception. "Oh, the humanity!"
Everyone expects them to explode, even if we have much better controls in place now.
2. Speed. Or the lack of it.
An airship can travel at about twenty miles per hour, under power, in calm winds. Less in most cases. At least if they're going to remain cost effective. On the good side, we can run them off of solar, using the latest materials.
On the bad, we're used to getting everything now. Now I said!
3. Initial investment for uncertain payoff. Without a large and obvious economic payday in the winds, few large companies (i.e. the ones with the cash to back such a project.) will attempt large scale airship practices. This may eventually change, if something better doesn't come along to replace fossil fuels, but until/unless that takes place, this will remain in the category of "interesting hobby."
4. Poor overall handling compared to modern aircraft.
They can't really outrun weather, and it's a bigger factor for them than for an airplane of helicopter. This means having the ability to tie down and deflate (Or go into a hangar) and good weather services, in most locations that the ships run in. This is really hard to do over the ocean, at the moment. That means being very aware of the weather. This is a thing we can do now, however, which will help prevent loss.
On the pro side:
1. They can carry very large payloads. Much more, far more cheaply, than any other form of air, or ground, travel. Especially if the system is worked out to run without fossil fuels.
2. They are in less danger of crashing and harming civilians than planes. They can crash, normally due to weather, but that was always rare. Once the explosion problem is taken out of the picture. They just move to slowly for that to be a vast issue.
3. Very smooth ride, making pleasure craft far more enjoyable. Comparable to a cruise ship, if done right.
4. Child friendly. Even a toy blimp or airship will be much to big to swallow! Yep, kids will love these things!