Sengoku period was just, like 50 years? Are they really using CK2engine on this? Not quite a lot of time to breed I suppose.
Instead, I suggest the Spring and Autumn period plus the Warring states period of China. Hundreds of years, lots of different factions/clans, lots of war, lots of non-war(e.g. Confucius and lots of different school of thought comes from this period)