The Pilgrim
Deity
Or you can throw in some sacrificial meatshields. Still cheaper than GE. Just sayin'... 

Can't believe nobody said this, but technological superiority works.
The main thing with the GW I find isn't moving more slowly per se, its losing the ability to rotate out wounded units out of the range of cities/defenders and replacing them with fresh units. This means that bringing superior numbers is of a limited advantage as you wont be able to use your second line of troops.
Thus, if numerical superiority doesn't constitute a big advantage, and manouvering is limited, all that is left is having better individual units. This means either having well promoted units (difficult) or technologically superior units, which is easier.
Took down the great wall from Austria in jungle and hills. They had pikes and crossbows, I had muskets and gattlings. Only losses I had taking both his cities was a knight that ventured too far forward on his own.
Has he got cities outside the GW ? If so, take those, I've only ever seen the GW surround 3 cities at most.
Attila's Court completed FP and all his other cities simultaneously finished happiness buildings and the Huns went from -20+ unhappiness to 20+ smileys
What does FP do, really? It says -10% unhappiness from non-occupied cities. But by my math, it looks like that includes puppet cities, too. Actually, maybe even more than that. I just completed it after I had almost 1/3 of the map, and my happiness rocketed up by 16 when I expected it to be only 3 (I included only population-based unhappiness in my settled cities). Instead it seems to have given back 10% of ALL my unhappiness. Seems better than the description implies by far--better than Notre Dame.
What does FP do, really? It says -10% unhappiness from non-occupied cities. But by my math, it looks like that includes puppet cities, too.