You're also supposed to be able to recruit wildlings (there's a tech requirement for that), ogres, mercenaries, and dragons. The dragon is only available (as far as I know) from the Curgen's Hold quest and then you have to research a very expensive tech. Mercenaries appear to be broken, you can build the camps but they don't seem to appear to be recruitable in the nearest town. I haven't tried ogres yet.
