Strategy specific units.

I know I already proposed this in General discussion but I wanted to propose it here too.

I got the idea by looking at some other guy's post in General discussion and what it boils down to is that rare units become available for purchase with certain strategies. some examples I already came up with are: Perfect defence: AT infantry, Relentless attack: Heavy tanks, Blitzkrieg: Light tanks, Sky menace: Fighters, Naval Commander: Battleships and Cruisers etc.
Also allow map makers to choose units to assign to each strategy.
Also allow it to be toggled on and off like more cities.