Just look at the speed charts, the most common LW fighters are faster than it is (P-51D, F-4U, Spit XIV, 109K4, ect...) and that is its only defense.....
"Well it is untouchable above 28,000 feet...."
The only reason people fly that high is to protect their perks, so removing the cost would bring them down and allow you to intercept....
I wouldn't mind a hit in ENY, which I think it could use....
(Many people argued against the unperking of the Spit XIV, and that wasn't the end of the world....)