Enable tank optics to be shattered by small arms. So something like a drivers view point armored glass can be shattered, but you could change it from inside the tank.
But if a gunners optic is shattered you will have to leave the vehicle to repair it.
Classic BattleTech has an optional rule for this, where you can arm mechs with paint sprayers and ruin people’s accuracy until they either submerge or have someone fire a water gun at them. Its actually kind of overpowered, which is hilarious.