Maybe it would be interesting to make a 'realm morale'. It would affect the realm in some ways, putting up (or down) taxes, or making more easy rebellions if too low, or some kind of bonus/malus...
Things would push up and down this morale: If you gain or loss regions, or battles. Starvations, looting, monsters, etc... would push it down, while Official religions and/or sacred wars (nothing better than to declare war against a heathen realm) would push it up... If you declare war against a bigger realm would put it down, but if you win a battle against it, it would put it up a lot... there are many possibilities!
It could be a flexible and somewhat realistic mechanism to push realms in the 'right way'...