These may have been covered elsewhere, or I might have merely done things improperly in my game. If so my mistake.
1) Vassals who lead/joined a revolt against you should be imprisonable and banishable to the wall for no tyranny cost. I had a Reynes of Castamere situation playing as LP of the Riverlands and a Frey led rebellion of 4 vassals. When I won the conflict, I only captured the Frey, and had to separately imprison the 3 other rebellious lords- each for a tyranny penalty. Then, sending the men to the wall gave me -60 tyranny each, while lopping off the head of the sole lady vassal cost far less. At the end I had a -220 tyranny penalty with my vassals, which doesn't reduce the chance of vassals rebelling the way that Tywin's even harsher actions did after dealing with the Tarbecks and the Reynes. The only non-tyrannical option seemed to be to have the Frey rot in jail and to not punish his co-conspirators.
2) This may already be in the mod, but I would appreciate it if we could send younger sons to the Citadel, the Faith, and the Night's Watch. It was common practice in real life to do this to preserve family claims and it appears to also have been the case in at least some families in Westeros (e.g. the Starks sent 3rd son Benjen to the Night's Watch, while the Royces sent 7th son Weymar, Aemon Targaryen became a Maester.
3) Being able to enlist son's who are being raised to command as squires to knights at age 10-16, a la Jaime with Ser Arthur Dayne, also seems like a nice touch. Perhaps it could be done through the guardian/educate system, tweaked to trigger events that affect personal combat, health, and martial stats as well as possibilities to gain combat related traits or those their mentor also has.
I don't know how this would affect game balance or how feasible the suggestions are, or perhaps these have already been looked at and implemented and I haven't found those features, but they all fit the canon and the atmosphere of the story.
