This is what my idea is, say a swordman is attacked by a behemoth, when the behemoth hits the swordman, he flies through the air and gets massive damage done and is temporarily stunned as he gets up and picks up his sword and shield, such a feature would not work on a battle machine though because its too large, so it would be a feature where units that are larger then others(the behemoth vs swordman) can send them flying so cavalry could trample infantry but be sent flying by catapults in turn, my description is kinda vague so if you want more clarity please tell me, I also had an idea where if the a units weapon affects its damage to a certain unit, for example the pike damages cavalry with extreme hp loss and unless the horseman has better range, he cannot attack from the front. this would be an interesting feature especially if incorporated for persians where the elephant could trample all but be weak against fire and pikemen.