Hmmm...to me, one of the things that should decide provincial availability it the overall faction "presence" in an area. We could have a very active or province heavy place in one area or another, but history at some point gives way to game balance. Increasing the provinces in the Lorriane/Flanders area is not as needed as say splitting Hungary or Poland. Also, based on the number of a faction in an area, we should have a certain number of provinces - IHMO, the number of provinces in a given theater should be equal to (number of participants)x3(+1). So if we have 4 factions crammed into one area, then we should have 13 provinces they should be fighting over.