I checked out the sky_city model and indeed, it is very complex for being a model for use in Morrowind.
I sliced the model into many smaller ones and saved each slice both as 3ds and NIF. I read that a lot of people had had problems opening the 3ds model, but for me it worked fine (3DS v 4.2), and I thought that by exporting it to NIF you could both use it right away as well as the slices being importable into more 3DS versions. The 2004 NIF importer for example works with 3DS v 5.x.
Everything is here
My thought behind it was that if you started working with the "main base" model, you could then add the sliced components you wanted by hand. So instead of having a circle with, say, 20 pillars "hardcoded" into the model, like the original did, you can set up five or ten as how many you want.
I've included the Tentacles and Cables on the download page for completion's sake, as I read that you didn't want them.
Either there is a problem with the original model or two textures was missing from the download I was given. See
this picture of the original model. The tentacles lack texture, but as you don't want to use those that doesn't matter, however; if you scan the picture a bit upwards, past the tentacles and past the first module, you see the chrome-like cylinders where there isn't a texture. If I understand 3DSM correctly, it was because that mesh didn't have a map. (this model is made up of many meshes, as any complex structure should be)
Now, I'm not an expert at modelling so when you check out the NIFs you might find they act strangely. I think it's because I cut out a large mesh, for instance a ring of 20 pillars, then deleted the 19 other pillars and tried to move the 1 pillar to the center of the grid. But I think that 1 pillar still thinks it is part of a ring, and if you rotate it, it might swing in an axis according to its old position. If you find that too hard to work with I think I can fix it.
I exported the NIF's with the option of 'keeping the original files' as textures. So you might need to hack the NIFs and supply the real directory paths to the textures. Or, if you want, I can re-export the NIFs with textures included in the NIF. It makes them much larger, and the textures are saved redundantly many times as many slices share texture, but if you don't mind about that then I'm sure NIF's with included textures are easier to work with. I'd also speculate that with a good zip program, the redundant textures would compress extremely well.
Let me know what you think.