I think if you add another map for a second player we can play multiplayer easily with low CPU usage.
For example, If we are on my map only my city will be visible. If I go to the right side of my map my city will disappear and my friend's city appear and My city stops to be a living city. And My friend's city starts to live for me.
For example, If we are on my map only my city will be visible. If I go to the right side of my map my city will disappear and my friend's city appear and My city stops to be a living city. And My friend's city starts to live for me.