Good idea. Another point would be to have different effects depending on what type of aircraft is attacking. If you're getting hit by WWII fighters, battleships and destroyers should be able to hit them with AA fire, but only modern units like the AEGIS should be able to defend against hi tech jets and stealth aircraft. This might take a bit of oomph away from battleships (they have too much power anyway). We may need more ships for this - a WWII class carrier vs modern carrier, to reflect the modern carrier's ability to defend against jets with its own jet fighters, etc.