I remember one guy posting a strategy: he would ring his cities with airbases, wait for the AI to move his air units (usually missiles) onto those bases in a vain attempt to attack the cities, whereupon his ground units would attack them!
I'm just saying: be careful of the side effects of airbases. They have been used before in middle ages scens as villages, and very successfully because of the stacking and production bonuses. I'm not sure if they would work as well as anything else.