It was a tough decision, but I had to go for the free-form play and goals as well. All of those other aspects are also important -- I'd call the variety of missions and combat settings a very close second -- but at least for me, what keeps me playing a game like this and saying "wow" is the variety in the game-play itself.
I want to see players be able to "win" the game in as many ways as possible. Maybe they win when they lead the armies of one kingdom to final victory over the other. Maybe they win when they become the richest landed noble in the land. Maybe they win when they lead a successful peasant revolt and overthrow the monarchy. Maybe they win by brokering peace between the two kingdoms and vanquishing the raiders once and for all. Maybe they win by taking over the black knights and starting off a ten-year reign of terror. Maybe they win when they become the undisputed tournament champion and win honors from the nobility. But of course, whatever victory condition they choose to pursue, they should be able to then keep playing after they succeed, and maybe work toward other goals.
I'd also love to see more done with the economy in the game. It already looks a lot like a closed economy, with raw goods being brought in by farmers, miners and overseas traders (or at least there could be, with the towns on the coast), taken to cities to be processed into intermediate goods, then taken to other cities to be made into finished goods. Having the movement and life of these goods -- and the money associated with them -- actually tracked would not only add to the game's realism, it would automatically bring in real consequences if, for example, cargo caravans were allowed to go unprotected from raiders, or if the player joined the raiders to attack the caravans, or if perhaps the cities themselves were attacked. If the available supplies of the finished goods in turn determined how many soldiers a faction could send out, the stakes would be raised even higher. The important thing would be coming up with a mechanism such that the scales cannot become permanently tipped -- e.g., if you managed to weaken all of the factions but one to the point that they died out completely, another faction would have to spring up from somewhere to make sure the player was still challenged. Also, player reputation would have to be observed, so that, for example, a player couldn't attack all the convoys coming into a town for a while to create a shortage, and then turn around and sell all the stuff they just stole to a local merchant for a huge profit.
Regarding letting the player become a landed noble, I think it's an excellent idea, but I think it'd be more fun if it were more than just a badge of honor. If the player acquires land, I think they should be able to actually make use of it. Put up a town, open up businesses, start some farms, whatever. They should also then have to defend it -- hire soldiers to patrol the nearby landscape to keep away raiders. Then of course, the best part: tax the people living on your land, and become fat and wealthy.
Personally, the other thing I'd suggest would be a lot of possible side-activities. When you get tired of slaughtering enemy war parties, it might be nice to be able to kick back and do some hunting, or go to a jousting tournament, or attend court and try to impress the ladies/gentlemen -- heck, maybe even start and raise a family. Just little things that give the player more stuff to do that aren't too hard to implement, but help round out the world and make it feel more complete.