I've long harboured an urge to run a game about managing a feudal realm. Obviously Birthright is geared towards this. But I'm thinking of doing one of those annoying smart-alecky rpg.net mashup things, probably involving Dragon Warriors (for the in-character level) and the "Seasons" rules cribbed from Houses of the Blooded for the resource management bits (shorn of any setting, because I despise the Houses of the Blooded setting the way I despise the Australian cricket team).
The first great difficulty with a feudal realm management game is intertwining the resource management bit with the role playing. How do you keep them integrated and stop it turning into a pen & paper and inferior version of Crusader Kings?
Clearly, random events help with this. "This month ... [sound of dice rolling] ... you recieve news that orcs are invading... [sound of dice rolling] ... from the south ... [sound of dice rolling] ... and a dragon destroys the village of ... [sound of dice rolling] Riverbridgetownplace." [Cut to in-character mode as the PC goes out a-orc-or-dragon-killing.] So of course does good improvisation on the part of the DM. (The character wants to clear some forest for farming so he can increase the population of his realm and get more money. Okay, go and persuade the headman of the nearest village to get his men to do that rather than, you know, do the work they have to do to survive. But it turns out the headman is a werewolf! Or whatever. Something better than that, preferably.)
The second great difficulty with a feudal management game is keeping all the players happy. Because whatever happens it's likely you'll end up with some level of irritation: you'll have to have one player be the boss of the others (if you're just playing in one realm, because that's inherent in the feudal system); you'll have to take 'turns' while the different players do different things (in the case of a number of different realms, or if you're in one realm with players taking different responsibilities); or you'll have to do something incredibly artificial (having all the players doing the same things together all the time, which is enough of a stretch when they're just dungeoneering, let's face it).
This is more difficult to solve. Playing PBP or playing one-on-one would seem to help, but the traditional group is going to find it tough to make the feudal management game work effectively. This makes noisms cry.