Has anyone played like this?

[HalfThere]

Seems like the trouble would come in needing to have large, expensive garrisons in many cities, and defending your gigantic borders against encroaching barbarians. Basically, it's economy moreso than anything else that would hamper you.

Even in my Alemanni game, where I've conquered Italy, I'm having similar problems. I need gigantic garrisons just to keep the Romans happy, and it's a real drain.

By the way, what difficulty settings are you playing on?