Hello.
I would ask for reconsideration for how the AI works. It doesnt build walls, though it follows some kind of pattern of building it's structures.
If so, what is the barrier for building the walls? It would improve the gameplay quite much. An option for it is to make the "radiant" system of building, by layers around the city center, as it is now for defense towers. E. g. first layer, randomly placed fields, houses, military structures and the last walls. Of course, if AI encounters natural obstacles, it will skip this place for building. Another option is to copy the AI behavior from Strongholds. Also, why it doesn't upgrade old towers to stone ones? At least, in my experience.