In my opinion, to really give the game longevity I'm thinking you could have a mode where you create your own character(if possible), and start off on the map as a sort of neutral character.
Now the game would play out just like the regular game, meaning you're neutral and you need to ally yourself with a side. You could start off with around 100-200 men (merc soldiers), and you could actually go to one of the Lords, whether it be Lannister or a Stark, and offer up your service. You could be sent on missions (need to be a big improvement over the crappy missions you're normally given) and could even ordered to participate in large scale battles, supporting the rest of the army. (the army would be ai controlled aside from your own unit of men.)
As you carry out missions and advance in rank you could be granted a knighthood or even a lorship, given your own castle and the ability to produce your own units, etc.
I was also thinking maybe developing some kind of rating system, not just for how certain factions view you but how certain hero characters view you. So say Jaime's army is being beseiged and you arrive to his aid. His respect for you would go up. I'm also thinking maybe have like a talking minigame...kind of like in some rpgs...I've always thought the diplomacy shallow because you could choose to declare war and all, but you couldn't actually have your leader say it face to face to his the other one. And likewise, the way you speak to/treat the characters in the game could have an effect on the way they view you... So if there comes a time when you are in trouble yourself, you might be glad you saved Jaime or were always courteous to Robb or whatnot.
Furthermore, I also think it would be very interesting to give you some moral choices. For example, if you let your men pillage and rape at will, their morale would be higher...but you would have to deal with a loss of standing with Lords like Edmure Tully and the like. Lower standing with an enemy could mean that your antagonist would chase you around the map in order to get his hands on you, and make every attempt to ambush or kill you, while higher standing could mean him coming up to you before the battle to ask for a surrender, or possibly even letting you escape if you were captured in the battle. (I figure instead of having your general die, he could get wounded and captured since he's your main character.) Also, different actions would have different impacts on different men. For example, if you often go into battle outnumbered, and come out victorious, then Jaime might take a liking to you, but his father might be the opposite, believing you to be reckless. However, if you are careful enough to not fight a losing battle, but ready to strike the moment an enemy slips up, then you might gain Lord Tywin's respect...etc.
I also think that the importance of the major characters in the game and the dialogue that you can have with them CANNOT be overlooked. Martin's series is as good as it is because of its characters. Without them the mod would simply give Medieval 2 a new coat of paint. The characters are the reason that Martin's world comes alive, the reason that I personally can hardly put the books down, and I think that if we really want to do the mod right, we should hold true to that.
Edited by The Prince, 03 April 2007 - 10:21 PM.