First off, any buildings with space players can enter is usually a bad idea since models dont block visibilty or seal the map. Existing building models are only used in the skybox and outside the map since they dont need to block player visibility. However if you still do want the models at least give some more detail since you havent exactly given anyone much to work off. Most models of this type I would assume would be made on a case by case basis based on the layout of a map, therefore any building models wouldnt be of much use outside the map they were created for, thus defeating the purpose of an asset pack.