If you play the DEI mod as Rome in Grand Campaign, you never get city garrison units that are combat roman military units ( the units you get by recruting from the barracks ). You just get very basic units such as Italian cavalry, italian swordsmen, slingers, town guards, etc. Do you think that's ok because it is a bit more realistic in the historical sense?
I never played DEI yet because my computer is a little outdated in terms of hardware. But I imagine you'd have a hard time defending a city ( either walled or non-walled ) from a full stack enemy army that brings units with high ranks of experience or some strong units.