No brigade-size armor unit could be moved by air transport during World War II because no country had a fleet of transport aircraft that were capable of carrying anything bigger than a cut-down light tank, and those required an often dangerous glider landing that got the glider crew killed. While the Germans did experiment with large cargo plane prototypes, they eventually gave up because the technology was not yet ripe. No-one had C-130s, C-5s or C-17s.JCS Darragh wrote:
. . . the only unit that could not be transported is the heavy tank due to the fact that it is a heavy tank.
Tanks traveled by road under their own power, on tank transporters (flatbeds) pulled by trucks, by rail, and by cargo ship when crossing water. With only a few rare exceptions, tanks did not move by air during World War II. And given the choice, they still don't unless it is absolutely necessary because of the stress it puts on aircraft engines and airframes. Moreover, there are only a handful of countries that can move a main battle tank by air in the year 2017, and only one or two that have that capacity to move an entire division (3 to 4 brigades, or roughly 300 to 400 tanks) quickly. Moving large numbers of tanks, of any size, by air during WW2 just didn't happen.
As for moving infantry regiments by air transport, let's also keep in mind that the combined efforts of Britain and the United States could only muster the required air transport to drop three airborne divisions (the equivalent of 9 to 12 regiments) on two occasions, and that was a Herculean effort both times (Overlord, Marketgarden). Most modern infantry moved by truck and transport ship; and a lot of it still walked in WW2.
All of that said, any proposal to add the new ability to move in-game infantry by air transport must be severely limited in order to maintain any semblance of WW2 reality. Moving more than the equivalent of a division (3 to 4 regiments) by air in one 24-hour period would be a good place to start the discussion.
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