An interestic point of 0 A.D is the battle formation of most of the faction in the game: Phalanx for Greeks, Testudo for Romans, etc. But, does not exist are battle formation bonuses, wich is a drawback because it´s necesary. Melee units die very quickly againts ranged units, witch make very hard to invade enemy city and forces the player to use specific units like cavalry, rendering melee units useless. The necesary solution is implement battle formation bonuses for each faction in the game, add defence bonus againts melee attack to Phalanx and testudo formation, and add defence bonus againts ranged attack with a shield wall formation.
Here an example of Celt shield wall formation: