Well, if you apply this standard, maybe the only strategic aircraft in the whole war was the B-29. Let's take the war in Europe. If you threw enough P-38s at the problem, you could have replaced the P-47 and the P-51. The P-38 wouldn't have done the escort or ground attack job as efficiently, but eventually it would have gotten done. Heck, you could even take an F4U, put 100-120 gallons of extra gas in the wings, take off the tail hook revise the supercharger gearing, and if necessary, remove two machine guns, and it could have escorted bombers into Germany.