Thanks!

True... missions that require to conquer and hold territory do seem like goals. I was thinking that they could add more depth to a war.
If the French invade and conquer London from the English, your mission would be to hold that city for an x amount of turns. If you fail the mission, the consequences will be bad. Your kings authority will drop, city's will gain unrest, and morale will drop significantly. This will simulate a population that just found out that their troubles and sacrifices went to waste or that thier king is incompetent. (They fought for nothing) If you complete the mission, that settlement will get a bonus of... "anything" that would make it worthwhile and keep a certain level of realism.
The offensive missions could also be an alliance type mission. Your ally is in need of help, they're being attacked from multiple sides. They want you to assist them by attacking one of their enemy's to lighten the load. If you complete this mission, relations will be strong and the allies will (almost) never back stab you. This could be active until the death of the current king of either faction. On the contrary, if you fail, the allies might hold a grudge or even break the alliance. Unlikely since they're in a bad situation, but still a possible option. Another alliance mission could be something like breaking trade rights with an allies enemy.
-Successful: Alliance strengthened or + in trade from regions neighboring
-Failure: Alliance broken or - in trade from regions neighboring
The idea is to give more rewards for completing such tasks. To make you concentrate on everything rather than just expansion. Kinda like what the mod is aiming at.