i just had an idea.
dome cities!
the planet can be relativly small, like a moon and devoid of atmosphere, so i wouldnt have to change to global skybox at all. that way i can use like planetary defense cannons and the such to spice up the mission. as for the cities themselves i can place a dome over them, make an outside dome with one texture, and an inside dome with reversed normals and a simulated sky employed as a glow texture. think of Cloud Nine from Battlestar Galactica. then inside that i can have the nifty little city. overall i can keep the whole thing compact, cutting down on relativly unused space that i would get with a large planet, and the player can approach it and experience the Star/sky transition in a way that flows and makes sence. in addition capital ships can hang in low orbit and bombard targets on the surface without the player thinking "how did that thing survive rentry? even better how come its not dropping like a rock?" hell its even a geat setup for some underground action. setup the structures as large subobjects over a large crater in the actual planetoid model, so if the city is destroyed it will leave a large crater. i think i can even pull off being able to destroy individual buildings. with the help of fred i can kill the glow maps and simulate all hell breaking loose in side. this reeks of cool!