Capture Points
It would be an interesting concept if the player bases were military camps with tents. While you would be able to capture prebuilt cities available on the map, and be able to upgrade them.
The cities can be of different culture, for example if you are playing as Mediterranean, and you capture a Mediterranean city you would get full features, while if you are of another culture you would get a handicap to its production.
This would allow for a more action oriented AoE game, and allow for better, and more historically accurate settlements.