Imagine a fantasy world where there are no horses, or trolls, or orcs... only humans and their bows and arrows.
This game mode plays out exactly like battle dawn, but with ONLY infantry. That means no dragons either. It would be mass chaos as literal thousands of infantry units swarm the map.
Perhaps that's too much, so we could add the cavalry. They're more expensive, but are weak to infantry. Might be a decent balance.