Update:
Good news! I'm just about finished with Prin Pahts. Here's what I managed to accomplish during this hectic month and a half:
I took Aloys' suggestion and scaled the area to 66% of its original size (i.e. reduced it by a third). This was a little tricky, in that I didn't want to scale the steps - they need to keep their same size; otherwise, they would appear too small. After scaling the rest of the room, I trimmed off the steps that were too high up. The outer stairs were no problem - they were able to intersect when the room got smaller. But the dias steps were trickier; I had to make sure the corner vertices lined up with the shrunken hub. Now the pedestals are only 5 steps apart. This also resulted in a reduction of blackout time during links between the city and Prin Pahts, as I was able to move the entire room up 100 meters closer to the surface.
This next step took a lot of time, surprisingly. I textured Besharen's pedestals, reduced the polygon count by a factor of 10, and fixed the vertex normals. Maybe some of you know this already, but the vertex normals for lit objects are based on the average of the normals of all the polygons to which the vertex belongs, by default. For smooth, round surfaces and objects, this makes the lighting look great. However, for objects with 90 degree angles (such as the pedestals), these averaged normals make the lighting look like it is coming from the wrong direction. So, I selected adjacent faces in the pedestal and split the shared vertices (with the Y key). Now the lighting looks decent. I combined the stone texture and the patterned texture so that the pedestal can remain one object. I then used vertex lighting to set the color of the pattern, according to the district. I then placed the pedestal in each courtyard. I only have linking books in the center courtyard of each district. As the city gains more shells, I'll add more linking books.
Speaking of linking books, I added Python code to show a linking book. When you are in my fake city above, it shows a picture of Prin Pahts. When you are in the non-mini-hub portions of Prin Pahts, it shows a picture of Ahra Pahts (v0.

. ANd when you are using a linking book on the mini-hub pedestals, it shows a picture of Janim's hub. The linking panel image appears to be too big. I believe the solution is to have an alpha border of 64 pixels or so around the main image (according to the linking image in Dustin's second age as a guide). But I'll tweak that once I get final images of the city and hub from Aloys and J'Anim, respectively.
I incorporated T. S. Kimball's D'ni numerals texture into the floor decals. I first colored in the outlined numerals and used anti-aliasing to smooth the edges of the curves. Then I added an underline in order to indicate the bottom of the numeral. [This is a liberty I took with D'ni numerology; it was difficult to tell which way a D'ni number was facing when you are looking at one on the floor from all directions.] I was unable to figure out how to make decals in Plasma, so I just raised the decal .1 meters off the ground, enough to eliminate Z-fighting with the floor. I made the whole texture 50% transparent, so that the tile pattern of the floor showed through, giving the impression that these are actually part of the floor tiles. I then placed a two-digit D'ni numeral over every number in the old map texture. *Whew!*
Side note: I am now an expert in Arabic-to-D'ni numeric conversions 
I redid the floor geometry in anticipation of Aloys' new floor texture. I replaced the square grid with a triangular lattice. I added a granite skirt around the edge, to help offset the map from the stairs.
I added footstep regions and fixed some collision issues. Finally, I darkened the walls and the stalactite-geode structure to make the area darker (taking suggestions from Aloys and PaladinOfKaos). I tried using vertex lighting on the walls around the lit crystals, but I could not get it to look right.
I decided to skip adding carved images under the linking pedestals in the mini-hub because it should be obvious that you will be linking to the top/bottom of the actual hub.
So, the only major item left is to replace the floor map texture. Other minor items include detail textures and perhaps an environment map on the crystals to make them seem shiny, and fixing some seams.
Pictures:
Thanks to all of you for your help and your suggestions.
NOTE: You are more than welcome to download and explore Prin Pahts; see the initial post in this topic. I have not yet updated the instructions for Trylon's new Uru age tool; I have to learn how to use it myself first.