Is there any sort of max size for a ship or station in the game?
With current tech, stations could be pretty much as large as you could make them. There might be some limitations, but a 5x5x5 km size station should have no problems. Ships on the other hand have more limitations, both on the actual design side. But once developers hit the technical limitation on the engine side, they might put their talented codes to the task to increase the limit. Currently, the biggest ship is the frigate seen in the trailer.