I) Make Outlaws more annoying and you cant just ignore them because they can loot and steal from your villages that you have not built defenses in
II) A recruitment system that isn't faction specific. So instead you recruit Villagers from Villages, Citizens from Towns and Special faction troops from castles
III) Upgrading troops should be changed (Barracks. see below).
IV) More stuff to build in your fiefs: Barracks(Can equip your villagers with chosen Armour, Palisade walls(for village defense against bandits), Watch towers(Village defense), Upgradable gate houses (Battering rams!), Orphanages(stops petty crime and increases happiness), Sentry's (sends out patrols and man hunters to nearby villages), Town watch (reduces crime), Hall of Honor (special units can be build from here) i could think of more but i cant be bothered typing them down.
V) please change the clumpy ugly interface and the dfff! sound when you click on menu's.
VI) Make many more animations for death/walking/running/throwing/shooting arrows/ jumping.
VII) Being able to be knocked off are horses
VIII) Overall the Campaign map and more generations for random battles by adding animals running around and birds flying about maybe some abandoned buildings.
VIIII) Theater mode
X)More tools and easier use for modders to make excellent mods
XI) Facial Animations
XII) Kingdoms Wealth and Population
XIII) A much more in depth trade system that is the main focus of all kingdoms to stay strong and feed there population with what they want. War isn't the only way
XIIII) Vassals and Kings should be able to die and new randomly generated (or heirs in the kings case) ones should replace them. They should be a more in depth personality system that effects how the vassal reacts/approaches things.
XV) New amours and weapons of course
XVI) Villages can be issued with what food they have, this effects what sort of people live here sort of like Anno 1404.
I could keep adding more but im sure they already have plans for m&b2 and i cant wait to see wat it has to offer