So under the new system it seems wars can create a great deal of unrest at home. This is realistic in some cases, but historically wars have also been known to increase patriotism among the populace. The surest way to get your peasants to support a war is to win it and bring back lots of loot.
Maybe there could be a victory celebration option. If you win a battle you can spend some gold and have a victory celebration. This celebration will improve loyalty, moral and control in whatever region it is held in. The number of regions in which you can celebrate a victory, and the amount it improves control will vary based on the number of enemy CS defeated.