We allready have the
http://ufoai.ninex.info/wiki/index.php/Base_Facilities/Missile_Battery,
It works by building it, buying or producing the Missile Launcher & Missiles, and then arming/equipping the Missile Battery.
The Base-Defense Laser turret is on hold pending development.
The real life counterpart is the THEL: Tactical High Energy Laser
http://en.wikipedia.org/wiki/MTHELIt's a chemical laser (like the ones in the game) thats been in development since the 1990s by the Marines and Israel.
My Idea is that the in-game Base-Defense Laser could be Purchased or Produced and then "Equipped" to the "Missile Battery"
I have also read that the ammunition for the "Aerial Laser Cannon" is to be freely supplied by the UN, we can use that system here to.
http://ufoai.ninex.info/wiki/index.php/Aircraft_Equipment/Weapons/Aerial_Laser_CannonThus the "Missile Battery" will become a customizable building; which is good because we can't yet destroy buildings, we can only reload a save point.