Rather than recruiting AI leaders to automate governing, the player recruits AI leaders to add to the number of worlds that they can personally govern. The answer: Send a governor to a colony to turn it into a core world. There are core worlds which are supported by colonies. There's a 'map of maps.' (Though you can customize the size of games and just play in just one sector.)
Put briefly(ish), with quotes from Stardock CEO Brad Wardell: GalCiv 4 will elaborate on GalCiv 3's interstellar empire building in some pretty significant ways.