I agree with this, but in the current state these guys are in it would probably take a while before they get to anywhere of that scale. I still hold out hope though! I also would like to suggest a few simpler additions to the game.
Perhaps a 6th even rarier resource than the wealth system? One that is usable on ALL of your cities and is able to buy possibly better stronger units? I wouldn't know what to call it, but it definitely would add a more interesting twist to the game and make it much harder to obtain than the wealth is.
My 2nd suggestion is a bit more trivial and more of a request than anything else, but please add some pens and little enclosed area's for our cattle to stay in. It is quite annoying seeing all of your cattle rampage through your city.