Clans spreading out is a problem in itself. The AI should try harder to consolidate instead they are willing to steal a province on the other side of Japan, and throwing ridiculous amounts of men to protect it.I think this could gridlock the game. What about clans that have their territory spread out in several places? What about two clans at war with each other but having a neutral clan in between? I'm not saying our system is historical but on the other hand I can't recall from reading about this period that armies on the march were all that restricted by clan borders.
In one of my Amago games I was able to hold against Toki (they were twice my size) for around a decade before they accepted peace. The AI was willing to travel through half of Japan, taking a lot of attrition to attack me through the straits between Shikoku (since they had some provinces there, I assume they were consolidating forces). In the end they got backstabbed by other eastern clans, because they were willing to commit all their resources to a no gain war on the other side of the realm.
The AI is too opportunistic and risk player.and most of those one province enclaves make it more in danger (from plots and the attention of bigger fish), than stronger.