I love all that old stuff - but we'd have to sign an agreement promising not to point at some 1941 drawing board prototype's projected speed for our favourite plane and say "why don't we have this in game - look! it's in a document you yourself provided!"
There are always dozens of different documents for each aircraft, projections, prototype trials, then tests on captured aircraft, etc. All of which take place under different conditions and with different biases. There's also differences of construction and quality of materials as the war progresses, particularly in Germany. Then you've got differences in gauges for measuring speed, climb, etc. - it's possible to argue forever over which figures are accurate.
Much as I'd love to see it, i'd be worried that if HTC released a portion of their base data, people would see it as definitive and argue 'til hell freezes over.
