I stumbled over some bugs and issues, though you might have already fixed these.
1) The walls of Minas Tirith and of the Hornburg provide the settlment with: "None"
2) There are no trade routes etablished between the harbour in Andrast and other harbours
3) River Serni course is slightly wrong. In game it flows past Linhir in the south, on the maps provided in the book it joins River Gilrain somewhat north-east to the city (or within the city, it's not that clear).
I also have problems to maintain order in conquered cities, if these are bigger and more advanced. I actually have to exterminate the population, else even a full-stack garrison won't be of any use. That's ok if you're playing the bad guys, but playing RK (and to a degree Rohan) this feels somewhat wrong. Problem might be solved if the "is_peasant" trait is removed from RK units (except maybe militia and bowmen).
Another things that frustrates me, is that the FMs do have a tendency to become real corrupt bastards. E.g. the King of the RK is a real glutton, having a 70% penalty on tax income. After the guys have been sitting in a city for some time, you'll have to exchange them (if you actually care). I think that the House-traits should prevent these negative traits to a degree, after all the Stewards have governed Gondor for a long long time without doing to much bad.
Furthermore they are amateur generals. Most of their command they receive due to ancillaries. Now and then I there's a "good captain" around but I never get a better general. It's somewhat frustrating to fight battle after battle, seeing no progress in the general's skills, rather he'll develop traits like "indecisive attacker".
I understand that you wanted to give an edge to the AI, but for the player it actually doesn't make a difference, whether there's a general or but a captain leading the army.