^^about a war with mehmed rather than hannibal, patagonia is 100% right : carthage has more land = bigger long term threat.
+ mehmed is in free religion, which means he is not gandhi's enemy, whereas hannibal is hindu
+ hannibal has bigger production capacity which we need to bring down.
About tactics, I wouldn't try to turtle up and wait for a counterattack. If we keep on taking cities, we won't need to defend.
Our army is brilliant in city taking, not in city keeping.
In fact, we can choose one of the 2 following options :
- killing units in cities to destroy his counterattack possibilities. This means targetting the capital. If we threaten his capital and keep destroying units there, there will be no counterattack.
- taking/razing smaller cities. If he takes them back, it's no big deal. We just take them again. Defensive troops = combat 2 pikemen and CD2 longbows. We have none of those things

.
About city specialization, I can only say that Atlanta is our money city

. If we take carthaginian cities, a forbidden palace in Atlanta is good.
I didn't notice any great hammer city, but I was too busy taking cities

(Seattle might be a good candidate for IW).
edit : cam, you're right gandhi has more power than anyone, but he is a chicken
