What you say is very true. Planes are their own units, so that isn't an issue. For AA, the range of AA we are looking at using is from 0-5. (From Cold War testing, we know you start raising the AA value too high, it becomes too lethal, especially when stacked like naval units will likely be). I had thought about it, but essentially you would see a unit "upgrade" from what it is currently to generally the same numbers except for the AA value maybe going from say 2 to 3. I can also see some attack going up with the addition of better radar for the US, but I am not sure if that will be a big enough difference. The other issue with such upgrades means the existing units have to have an upgrade. That can be extemely difficult to pull off with the Civ 3 engine and still not have it that the unit can be produced or to have say a Portland class CA morph into a Baltimore class.