I disagree with the choice of leaving the Night's Watch out. If it is possible to make sure they are in a locked war with a Wildling faction and unable to war against anything else then they should exist. The reason I say this is two fold: Even in the second book a lot is happening beyond the wall, not as much as is going to happen I'll admit but still. This means that the Night Watch is an important part of the book, one of the main characters is in it after all, and has plenty of interesting stuff going on. The second reason is that in a game of A Song of Ice and Fire the one thing I would want to do the most is join the Night's Watch. Something about small bands of elite warriors has always fascinated me.
I believe that the Night's Watch would serve very well as an escape from standard Mount and Blade formula to allow for a more structured quest and ranking system. With less variables and much smaller numbers it would be interesting to see the player being able to gain ranks so that they can control a few warriors then eventually raise to the rank of Lord Commander and control the entire Night's Watch.
Note that there is no use trying to stick perfectly to the books. What you want to do is start the game as faithfully as possible. But as soon as a player enters the game everything will change, and bugger what the books say. So you should allow for this and create the ability to change things: say if the player becomes Lord Commander they could strengthen the Night's Watch and take it to war into the north (as in the books) or turn around and attack the south (at what consequences).
Anyway I'm just ranting. This mod is amazing, the most successful of the ASOIF mods that I've seen so far. Keep up the good work

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-Munchkin9