There really is a mod for everything, no matter how obscure and potentially silly the idea might be. With mods you can add new units, new starting positions, new factions, a complete balance overhaul, a variety of new battle maps so you're not just fighting in an open field every time, and the list goes on for a while. If you've ever gotten invested into a Total War game you probably know just how important mods are in keeping the whole experience fresh and interesting.