I've seen many threads on the topic of what civs have been left out, but i have never heard mention of the assyrians. They should at least be worthy of consideration, they conquered a vast empire consisting of all of Mesopotamia and ancient Eygpt around 700 BC. They built roads and improved trade throughout their lands as well as deporting differnet peoples to different areas effectively destorying those civilizations. The Babylonians ruled the same area for less time and their included in the game. (I know about the law code and other important advancements but its possible that the assyrians had huge influnce on those documents considering they ruled the babylonians for over a century)