Ok. Got a weird idea but i think it will work. You give the unit a battle drone upgrade (the shield upgrade) and it will surround the tank wherever it goes. Give the battle drone the paladin laser, and condtionstate=attacking will make the drone visible so you see the transparent shield, while when its not attacking it is invisible (no model). Then you make the paladin laser deflect everything, and have the highest ROF. BUT the laser will have a certain clip size so it can fire so many lasers to deflect a certain ammount of things that it will run out of ammo, and the shield will permanently be invisble (because its not attacking) Now the tank is vulnerable to fire.
But heres the cool part, make the tank able to go back to dock at the shield generator so the drone can get its clip refilled and shields recharged, like an aircraft.
Sound Good?
If you need me to rephrase anything just ask, but i think in order for the paladin laser to shoot things, everthing must be a projectile object.