Flak towers?

[IceFire]

Idea popped into my head (which is always a bad thing )... what about flak towers? We've never had them in the game before. I'm not even sure if anyone in MOD land has ever created one.

These are what I'm talking about.

http://en.wikipedia.org/wiki/Flak_tower

I realize they were for city defense... but I thought some smaller ones were used for airfields too? Perhaps they could be created using stationary ships or armor with the necessary weapons already on them?