I have tried many times to envision this system. The most detailed look at it is in the GURPS pub.
I have that supplement, although it's packed away at the moment, so I'm going to go by memory here (as well as the TravWiki page on the system, which I think generally agrees with the book). In a couple of days I can dig her out and confirm or deny what I'm about to post here.
THAT many people stuffed mostly onto one belt (the outer belt being much less populated) would be a daunting prospect.
The Wiki (again, rumored to be based on the GURPS book) says that the outer belt has a population of around 3.3 billion people, or just less than 40% of the total system population. That's less -- but definitely not much less -- than the main belt.
Unless there were many large asteroids (unlikely due orbital mechanics) means that construction is on the surface of most.
Why would orbital mechanics dictate this? Our asteroid belt has over 25 bodies above 200km in diameter, and 3 that are over 500km in diameter (Ceres, Pallas and Vesta). And at just two asteroid belts and a gas giant in total, I would guess that Gliss System's potential for perturbations are much less than Sol System's.
Now by sheer numbers, the vast majority of asteroids are going to be smaller clumps of gravel. But in terms of overall mass, these big asteroids clearly have the lion's share of resources, and they are generally solid chunks of... whatever they happen to be (it varies). Vesta, for the record, is the densest known object in the Solar System.
Transportation would require huge numbers of craft.
That it does. And that is why the Gliss System's transportation authority is the
de facto (if not
de jure) government of Glisten.
If jump shadows are in effect that cuts down on jumping directly to/from many parts (I don't know how many AU' out the main belt is).
Well, it gets a little murkier here. The Wiki page (and I bet the book) says the inner belt occupies the Habitable Zone of a class G3V star, which would place it in generally the same orbit as Terra (Traveller orbit 3, or 1AU out). However, the Wiki page for Glisten (the world) claims that it is a K9V star, which would place the Habitable Zone around Traveller orbit 1 or 2. Jump shadowing might be a more likely deal with the latter, although that star is considerably smaller than the former, so maybe not. And, of course, those inner orbits are much tighter too, so anything on them is easier to reach anyway.
There's also the matter of that gas giant. It occupies the orbit immediately out from the inner belt, as well as immediately in from the outer one. This is going to affect the orbital dynamics of both belts considerably. Depending on the age of the system, there might be a lot of good real estate parked in the Lagrange points (for the inner belt) or in some sort of orbital resonance position (for the outer belt) of the gas giant.
At any rate, the Gliss System is noted for being a collection of isolated, semi-autonomous, highly variable societies federally connected by the transportation authority. A US of Rocks, if you will, with Glisten proper being the California (or Texas, or New York, or whatever you prefer) of all the rocks. This would make sense if, in fact, some parts of the system are much less convenient to reach than others.
It would be nice to see a new treatment done on this with a view towards taking into account the actual scope and pop size coupled with the TL F.
I thought the GURPS treatment was pretty good, although I concede there's always room for improvement. For what it's worth, here are two takes I have on the Gliss System:
Gliss is a T Tauri type star, a main sequence dwarf star that is less than 100 million years old. This would explain the rather... basic setup of the system, with the two asteroid belts being in reality a small accretion disc with a gap where a gas giant is plowing through it. The missing orbits ('donut hole') in the center of the system might be a bit of a mystery here, but perhaps it's explainable by early system catastrophe (like a gas giant forming and then getting dragged into the star right off the bat), or maybe the dust in there doesn't have enough mass to form decent accretion material.
The inner belt is the blasted remains of a casualty of the Ancients Final War. Yeah, I know... THAT trope; but it makes more sense here than in other cases. Consider the fact that it's a debris field orbiting the Goldilocks Zone of either a KV or a GV star, both of which are considered excellent candidates for hosting Earth-like systems. And, of course, Canon does at least imply that The Marches has more than its share of these cases.
Either of these interpretations would make the system valuable to industry and researchers alike. A T Tauri Glisten would have a much higher metallicity than most systems, and as such it would have that much more exploitable resources. And astrophysicists would no doubt make a point of having observation posts all around the system, particularly if Gliss were at some unique critical junction in its evolution (say, for example, it was just beginning to fuse hydrogen in its core). This might even explain the confusion over Gliss's spectral class, as T Tauri stars are brighter and more bloated than they will be when mature.
Of course, an Ancients-wrecked terrestrial world Glisten should probably have more exploitable resources than a typical asteroid belt too, since it probably had more mass to work with from the start. And of course there's the possibility of the occasional artifact.
