I think someone has made a proper MD-80. At any rate, there's one on the market already. I think Captain Sim ought to be thinking about plugging the huge gap where a classic 747 would fit, but they would have to get the INS issue straightened out. The DC-3 was a hugely significant aircraft, and some are still flying. Captain Sim could really capture the character of this airplane, and, again, there's not one on the market for FSX that I know of.