If anything the only suggestion I can make, as I too have noticed a bit of "stagnation" (playing the Crowned Stag Scenario as prefer to kind of always start out in peace team and let things develop), will be defiantly to add more flavor events and building options since it seems you've formed a good working relationship with idib816 (Prince and Thane Mod)
The problem of stagnation depends on several factors IMO
- ruler traits, Targaryens are more "unstable" than Barethons("madness trait")
- high fertility and low mortality of newborn babies
- rulers high life expectancy(60-75 or more)
So, if you have long live king with good skils and traits you are unlucky and boring game for many years
On current patch(mod wersion) Westeros is more stable Robert almost always wins, and that the reason