I doubt that the objectives of minor factions are territorial. In Warband, factions without territory were eliminated. If that mechanic persists in Bannerlord, minor factions would need to be excluded from it or they would die out too soon. Published information about minor factions suggests they are each a dedicated enemy to a particular major faction (guarantees war during peacetime) and some/all are available for hire as mercenaries. While they fight major factions, I doubt they act like them.