on top of no self-sealing tank, the zero also had most (if not all) armor plating removed around pilot and engine which gave it the speed/range/agility for which its famous. We model this with plane reliability, so if you make a plane where you boost all those above things without also improving reliability you'll have a lot more downed planes in action than if you had. may be worth the tradeoff though, who knows. It was for the japanese in the short term I believe.