Not quoting anyone because several people have made good points. The key to fun is team play. The duchy is the most immediate unit. Then the realm. Then everyone else. That is the secret to fun in BattleMaster. For everyone.
Wouldn't a region be the most immediate unit? Most are too small to make a difference by themselves, but I've also seen small, unimportant regions become a thorn in a realm's side.
Just nitpicking. Your overall idea is right, imo.
