I think the reason that the major nations only have one region is that we simply will not be allowed to conquer them piece by piece anymore. They will remain intact for the duration of the game, which is accurate. When a nation is defeated in war the victor will be potentially rewarded with money, trade rights, some sort of protectorate status for loser, or change of government, including other other possibiities. The settlements and structures that are scattered around the countryside are an attempt to make the owning nation come out from behind fortresses to defend these vital targets, thus creating more field battles. I imagine that if a nation's Capital is captured and held for a few turns, peace negotiations will soon follow. It is the smaller factions, mainly in Germany, Italy, and overseas Colonies that will be targets of outright conquest. That's my take at least.