I don't think it would be. First, how do you tether it? What with? Where do you put it? (Over a city would seem to be the most logical place, but what happens if the tethers break?


)
{first} We would need a tether that includes multiple freight/passenger elevators, the elevators must be designed to remain upright, while ascending/descending within a non-vertical (the tether will not be perfectly straight, ever), moving (it will not be perfectly still, ever; re moving air masses, at different altitudes/speeds/directions) hollow tube. This sounds more complicated than it probably is, but then too, we would need to know how such a tether moves in various wind conditions, to get an idea of how long any given section of a tether can be between platforms. Say for instance, a tether is good in any normal wind conditions, with acceptable tolerances in vibration/swaying motions, for a length of 1km. If such were the case, then a platform riding at 10km would need to have 10 small 'platforms' for firming up the stability of the tether all the way up to the main construct. You'll have to find someone with the proper engineering/science background to answer the second part. I wouldn't put these above inland cities for the most part, but rather offshore. One thing that ground based ports/air ports have in common, is the cost of the land that they take up, but not so with these. If the tether breaks? Something like what happens when a huge skyscraper falls, I would imagine, IE, was the engineering insufficient, or was the disaster caused by some other force? In either case, would we see changes made, and newer and better constructs built, or the end of the concept?
And there's the issue of delivering freight & passengers to it. I imagine a funicular up the tether(s), but is that cheaper than landing the airships at a conventional (more/less) airport?
I would think that getting to and from would be very cheap, fast, and cost effective, assuming that the whole tether system can be built in the first place, that is. If we lack the material sciences to built something light and strong enough, then the idea is stillborn, but considering our lift capacity, I doubt the weight factor will matter at all.
Postulate a craft 6000' long & 1000' diameter, or a volume about 55x
Hindenburg's. What would her freight lift be? Is there a market for moving that much cargo at around 200mph as cheaply (almost) as a freighter? I think there is. Airports will have to be redesigned to handle that much freight at one time...given the "flying airport" isn't in place & able to. So, too, if they're to cope with 2000-4000 passengers
per airship.
Oh, I agree that freight that can be moved 10 times faster than by
the fastest merchant shipping, and can ignore geographical restrictions regular ships cannot, is likely to be a huge market, but...Using your own figures, you now have lighter than air airships coming into an airport that needs to eat up far more costly land than what we now have, and this doesn't address any of the OTL problems with surface winds common to all airships, with or without better lift capacity from improved material sciences.
And how resistant to storms/high wind is it? Or is it winched down if really inclement weather threatens?
I was rather thinking in term of the platform being
above the weather, not in the weather.
I have not gotten your best guess yet, so I don't know what ball park is within your thinking, but...
Say that the OTL hindenburg's 215 tons weight, is 160 tons of frame. I don't have any clue, so this is just a number off the top of my head, but going with that...
So, our OTL Hindenburg's weight now has it's frame weighing in at a mere 16 tons (As per you OP), so 215-160=55 tons weight not reduced by better frame construction materials. We now add: 55+16=71 tons weight, and arrive at the ATL Hindenburg's weight, and this subtracted from the lift capacity of ~232 tons, gives us 144 tons usable lift capacity, while retaining the original 17 tons safety margin. These numbers, if my groggy mind is doing the math right, are based upon your premise, and my USWAG (
Un
Scientific
Wild
Ass
Guess), so feel free to swap these numbers out with your own.
In other words, the OTL Hindenburg could haul ~11 tons cargo and about 90 people & all the junk they needed, whereas your ATL Hindenburg could haul ~144 tons. As these are just very rough guesstimates, lets just simplify it to say 110 tons, or ten times more. Thus, the Giants you mentioned up thread, would be able to handle ~6,000 tons.