I'll post these mission and event ideas here.
BRIDGE DEFENCE
You could add bridge crossings (and preferably lenghten the rivers to the mountains) on the map. Player (when high enough rank on a faction) could get assigned to defend/block a bridge crossing for a certain time. There would be a high chance of some enemy group trying to invade player's territory trough bridge. Mission could also be to clear bridge crossing from enemy/brigand band (no trolls

) that harasses/taxes merchants or anyone who tries to cross. There could be a general hide option added to the game for groups in the map screen or this could be used in this kind of scenario only. Hiding could shorten player group's spot distance severely.
River should be so deep that swimming would be required to cross. Only lightly armored units could swim across. Maybe making of swimming animations would be too demanding in relation to the gains here, so maybe crossing should be only over the bridge.
Now if it was possible to hire effective missile units to shower enemy side with arrows and pikemen to block the bridge entrance it would be sweet indeed.
VILLAGE DEFENCE
This would be possible if there were small villages, where you could buy food (and other simple stuff) and hire peasants.
This could be a ripoff from seven samurais (or magnificent seven) film(s). Villagers would ask player to defend their home from pillaging bandits. There could be only few huts to indicate it was a village. Or better yet if AI has a hard time to avoid riding into buildings, there could be a wooden palisade with one open gate. Area inside the palisade could be the size of the arena in Zendar or even smaller. Outside area could easilly be very flat and barren. AI should avoid inside area of the palisade when on horseback (like it was impassable mountain etc). Bandits would be able to walk trough the gate on foot. Bandits on horseback would dismount when enough enemies would be killed outside of the palisade and attack trough the gate.
There wouldn't be much of a reward, but maybe some villager (if he/she didn't die) with unique skill(s) or abilities could try to join player's party after the bandits were driven off/killed. Alternatively there could be some unique or good item or thing. This could be for example an extraordinarily fast and maneuverable horse (not warhorse though) or some useful information. Weapon would not be an appropriate reward from peasants.
CITY DEFENCE
City lord assigns player to defend city from incoming enemy warband. If larger battles could be done player would begin the fight outside the gates (if he chooses), and when losing a combat phase, would be forced to begin next phase from inside the gates. When starting a phase inside walls enemy has penetrated the main gate and would be pushing in trough it. Player would have to clear the inner yard from attackers. This inside yard don't have to be very comples with lots of details.
Since slower system computers cannot handle massive battles on open terrain this scenario could take place only inside city walls. In this case player wouldn't be able to move outside city gates and the small glimpse of outside terrain would be flat and void from trees and such details virtually no external terrain wouldn't have to be drawn.
I can play ok with largest battle size, good combat AI and all video options enabled (1024x76

with 1.4Ghz Athlon and GEForce 3. I think much larger battles could be done if the terrain was more flat and void of details. Or would AI take too much CPU time?
If larger battles could be done player could begin the fight outside the gates, and when losing a combat phase, would be forced to begin next phase from inside the gates, as described above.
ESCORT DUTY
Player is asked to escort some important person(s) (daughter of some lord, nobleman, holy person etc.) to wherever. Maybe this person is riding on a horse or inside a closed four-wheeled horse-drawn carriage. In latter case enemy footsoldiers could move to side of the carriage, open the door and reach/hit inside to knock out or kill this protected person. Now comes the part where it gets intresting; If player's side runs out of soldiers in a combat phase and enemy soldiers have reached inside carriage they could disengage from battle holding this important person as a hostage. Player could have a hell of a time explaining to appropriate lord why his daughter was taken. Player would be demoted...big time or even kicked out of his current faction. Carriage would not neccessarily have to be mobile. It could just be a fixed object in the battlefield, though preferably in a road and not in a creek or in a ridge.
GOLD CARAVAN ESCORT
When reaching high status in a faction player could be offered to escort funds to somewhere. This is basically the same scenario as person escort above. Enemy could snatch the reinforced gold carriage and try to run away with it at reduced speed.
CLEARING ENEMY GARRISON
Player is commanded to reduce or kill enemy garrison or outpost protecting some city or location before final assault.
REASSIGNING OF PLAYER'S TROOPS
Some rare occasions city lord could decide to take some soldiers from players party to reinforce city's garrison and/or patrolling groups. This move could be influenced by player's unit's low morale, players low rank compared to his unit quality or bad situation with current garrison and nearby patrolling units. In the game player soldiers would whine to city lord about player's bad conduct and/or enemy has killed lots of patrolling units near city or in it. Again for the record player should not be able to hire higher grade units than he himself is. This kind of thing could happen easilly if player has been just demoted.
TOURNAMENT
Player demonstrates his skills with horse and lance, swordfighting and archery. Archery targets should be placed in random distance so that player couldn't train this.