Well, what you will need to do first is to choose how many teams you will creat for your map. Like Roman Empire ,Greeks, etc. Next you will need models for every era. Also maybe you should remove the mana from your map if you want to make a map like Age of Empires. As for special abilities maybe you can make some teams to have a dmg boost when they are on defense, for Modern you can make some buildings that can create ultimate weapons like a nuclear bomb, maybe you should remove the food limit from your map, a trade sistem that will let you to trade gold for lumber and lumber for gold.
