[heloguy]

I think it's important to remember that date of manufacture, and date of field employment are probably very different things. Hell, it's still that way today with A/C mods in the U.S. military. It's very likely that even though the auto prop mod was on new machines, those machines were probably slow to filter to the working units. Same with the retro fit

In any case, the best option is to have it selectable as another airframe. The rocker switch on the throttle could also be another variant given that we have anthromorphic control as an option, although I suspect this was part of the auto mod. Either way, as far as online, servers could set how many of each type are available. Offline, the user could choose or be assigned which type according to rank, or availability (if we get a dynamic campaign).