As a ten years AOE3 player，IMO the first thing should be the remake of the unit models .AOE3 have beautiful graphic but when you zoom the camera closely, the models become too rough.
Second, the artistic design of European empires are too similar.Even Ottoman have only a few unqiue building models and unit models.Wish original European empires in AOE3DE could reference a little ideas from Warchief and Asian Dynasties.So the whole game could have uniform style.
Third, remake the card system.Waste time to unlock cards is nonsense.This is a RTS.Just give me all the cards at first and delete the low level cards. Also there are too many underpowered cards. Maybe very fun, but underpowered.They will never have any chance to be used in PVP game. What a waste. Please combine some of them and redesign some of them.So the card strategy could be much more various.
Four,new civs please! AOE2DE have 35 civs. At least give us 2-3 new civs.Personly, Persian empire will be amazing.Also a new campaign about the war between Safavid and Moghul will be interesting.
Five,redesign some extremely unhistorical elements.For example, Janpan have the most powerful Musketeers, even more powerful than British, Ottoman and Moghul.What a terrible joke.