1: USE OF MORALE: Alot of strategy games make use of morale. It could be when a solder or troop are surrounded, Thier morale would reduce (effect of morale maybe -1 or 2 attack) And the surrounding troop morale would increase (maybe +1 or 2) attack. Or when losing morale becomes low and winning side has high morale. This will make strategy more flexible
2: CAVALRY CHARGE: Cavalry has been the greatest and most feared troop during the Cold weapon era, not only because of Thier mobility but also because of Thier ability to charge at enemy(ies).
This could be implemented in aos ( for example) when there is three(3) or more space in a straight line between a melee cavalry unit and other unit the cavalry could charge at enemy unit (charging can result to maybe +1 or +2 attack). It increases virable in battle.
3: A COMMANDING UNIT: This can be a unit ( no need to be op or anything more like the avatar of the player in the game) whereby if this unit is killed the killed commander troops would have low morale and the killer troop will have increased morale ( this is to make ninja, assassin and such type of troops important) Maybe add a activate/deactivate commander button.
4: ALLIANCE: Who doesn't want to have friends?, Make a button whereby you could send alliance request to other players in multiplayer or AI in three or more user campaign, the alliance request can be accepted or rejected can also be cancelled after some turns (if you like, or if you want to backstab your ally

This is the little I can currently think of if I have anymore ideas I would put it down.
THANK YOU FOR AOS.