This is a very cool idea, and i really cannot come up with any reasons that it would not be in AA40E except lazyness. Its a cheap piece that could add alot the the european battlefeild.
Anyways if it was to be included in AA40, then I like Razors rules the best. 15 IPC, land units move one extra space, Max damage 6, and with 3 damage it cant increase movement.
Other people have intersting ideas, yet i think their to complicated and dont add that much detail or accuracy( and I am some one who thinks historical feeling is very important to my enjoyment of the game) or are contradictory to the spirit/play of the game.
Flashman is obviously true in saying that given 3 months a division in france can be transfered too the eastern front with ease. However if strategic land movment was infinite, then sea movement would have to be changed aswell. Flashman often advicates for the corssing of the atlantic too take 2 turns, and while I understand this gives uboats a shot at taking out convoys it makes no sence at all when armies are zippping around europe and siberia.
The limiting of increased movement based on IPC value idea is interesting, however i dont see how it adds more strategy to the game and i dont see how it is going to add a significgant amount of realism to the game compared to the originaly rules proposed by Razor.