Honestly, as a Player of the original Age of Empires 3, I can only give you devs one advice and you should consider it important for you and your game:
-> Fix the gamebreaking bugs
- Sync Errors
- Game breaks, crashes, disconnects, whatever - Let the player REJOIN the match no matter what (like in Leage of Legends)
- Why does the mouse disappear for so many players?
- Fix those bugs, dont blame some firewall issues or whatever, like it was done in the past. Do actually fix them (best before release) or this launch will be a failure and the game will end like the original AoE3
- Honestly, just mentioning the 2nd point again, because its really important, work on fixing the dcs, crashes etc. and make a reconnect actually possible, the games tend to be long af and its frustrating, when people always dc or the game just flatout crashes or gives you some nonsense sync errors, which shouldnt even happen in the first place, if you get the hosting right and prevent players tinkering with any important files.
- Do not save homecities etc. locally.