You know what I think would be good, take this idea of capital cities and make that the defacto dock of that planet. Make second dock on another part of the planet to signify a different part of that planet (the Council/Brigand example comes to mind) and depending on the RP of that planet maybe some will have diametricaly opposed forces on a planet but with careful consideration of which ones to avoid too much overbalance on one side over the other.