Actually if you rush towards newer siege units then you can easily take cities without worrying about this. A good example is when I took two cities in four turns with three cannons and a musketman. I was the most technologically advanced and so I rushed towards chemistry to grab cannons. Korea the technologically inferior wasn't expecting cannons. --- This is minecraft. Why would you want to deal with uneven terrain? If you don't like the lay of the land, you punch it until it shapes the f*** up.
Well, I was trying to use The Huns' Battering Ram because I thought it would give me a nice early rush advantage, but by the time that gets to the city it's already destroyed. I even used the old ploy of sending in weaker military units as distractions, but the AI somehow grew some intelligence with this expansion and targets my siege weapons first.
I decided not to crank out new siege units until I had the Armory so I could throw the Cover upgrade on there. That solved the problem.