Well, I dont know that much about modding bl spicifically, but it seems to me if you took the tank data block, and replaced the tank model with your model, WHAMMO! Some what of a mlrv. you could then go with my idea, where 4 missiles sit exposed (or protected, w/e you feel like) on the sides of the gunner. That way you dont have crazy scripting errors or any thing. Cuz if you move the tank turret, the barrel moves up and down, not the gunner. All you have to do is make the barrel your missiles, and it should look fine after some tweeking.
Btw: you should make a bunker buster next