In Age of Empires II, when you create a unit like for example a couple of swordsmen, they have certain attack and armor properties. But these properties of the existing units you’ve created will improve when you research attack and armor in blacksmith. Even if you upgrade the unit in the barrack to twohanded swordsmen, the existing ones will immediately see this effect.
However, I think it would give the game more depth and decision take if the researched unit upgrades were not applicable for the existing units, but only for the units you’ve created afterwards. That way you could make a decision to create a unit before the upgrades or wait until the upgrade is done and then create your army. For your opponent this would be a task to find out if you have created an army already or if you are planning to upgrade first. That way he can anticipate that to either create an army immediately so he can have an advantage and a good opportunity to beat you right away or to upgrade too to not fall behind in the late game.
Also I like the way that in Starcraft 2 you can see wether your opponent is upgrading or not by just looking at the building if it is shining. That way you can directly change your strategy in order to anticipate the next move. I’d like to see these kind of features too in AoE4.
What do you think?