currently the rebel provinces are empty because when i made the first incarnation the rebel faction was very rich and very very aggresive,
i keep trying to determine at what point the clan factions begin expanding by monitoring what triggers their aggression and adjusting their start buildings and units accordingly,
i have noticed that increasing the difficulty level changes what they "want" in their provinces before they get all aggressive,
try switching -ian on, (see command line switches in repository forum) and then hit G in game to "see" all provinces - you may notice quite a few battles,
around 60 years in the factions start getting killed off until only one or two eastern factions remain, and Hyuga is genberally controlled by only one clan at that time, then they will pause and build up before they resume annihilating each other, and both the west faction and east faction then turn on the central factions (oda, ashikaga, ukita and mori)
basically we want the east to remain peacefull as long as possible, they have an economic powerhouse over there and they can quickly swamp the west with large amount of troops,
the AI builds ship looking for invasion opportunites and to prevent themselves being invaded, also trade can be a big big boost to income and they want that boost as well.
but sometimes they do go overboard - am going to lower the build priority of ships a little - have seen huge navies of 2 or 3 full stacks sailing around...