I was thinking of long haul so that means a large ship carrying hundreds of passengers in the comfort of a hotel, not a carbon fibre gondola. Space is at a premium in conventional aircraft but not in airships.
First Weight is always at a premium for aircraft even airships So a Carbon fiber gondola will be needed. however the low speed of an Airship, max speed under 100 MPH
This is What it sounds more and more like
A Cruise Ship in the Sky.
You would be flying at an altitude of 1500 to 2500 metres so you will be able to enjoy the scenery. And if you are really in a hurry you won't go flying but take to the internet. There might be a market to develop a supersonic small aircraft with global range or slightly less but I would be surprised.
It's not a true form of Transportation more part of the Destination itself. You are well to do want to go on vacation so you board and along the way enjoy yourself make a few ports of call enjoy a few days at resorts reboard, move on the next stop. This is in some ways the same idea I am talking about, but it's not so much transportation as tourism. It's the Hindenburg crossed with Carnival Cruise Lines.
Supersonic transports are just not realistic in the near term. They are like the Brazilian Economy Always the land of the Future.
What do you do when the weather turns bad in Hawaii or another small area? I wouldn't want an airship designed for that. Use STOL aircraft for such work. Your airship might have to clear out for perhaps days before resuming service.
You have the Same issue with a long range Airship. It's easily pushed around by the Winds and Weather. If you have a storm on the route you need to change course or land.
Let an airship have the choice of several landing places connected by a high speed rail network. How often does it happen that Cairns and Adelaide and all places in between have bad weather, storms or thunderstorms? Of course a halfway suitable railway net now only exists in China, Japan and Western Europe but that is a matter of time.
being blunt For long range travel A fixed wing Aircraft is far more efficient in speed of travel ability to power through weather then a airship. You can try and say more fuel efficient and it is. but people looking to travel at ranges don't want to spend days on trips, unless the travel is the Trip. If you are a business Passenger in the 1930's a few days on the Hindenburg from Lakehurst to Frankford was a revolution in travel. Today No. Most people traveling don't have the luxury of time. Thats more a vacation/Tourist thing.
And the "environmental and Fuel efficiency" advantage would be tossed out if half the travel market is going supersonic.
as for Railways There are still parts of China, Japan and Europe without Rail. High speed Rail in the Americas is coming but like all things it has detractions.
In any case we are also starting to see Hybrid technology moving into Aviation. Using Electrical power combined with conventional jet propulsion to increase efficiency. by the 2030's They are already working to platforms that use electric drive.