Record your replay with a helicopter. Start watching the replay, pause the game and paste the following code into the debug console, then press "Local exec". Voila, our replay helicopter now has animated spinning blades and sounds.

Code:

_list = player nearEntities [["Air"], 50];
heli1 = _list#0;
heli1 engineOn true;


The code above is for a mission where (during replay) you are alone in front of a single helicopter. Modify as needed for other missions.
Extra faff- yes, but still much MUCH easier than the alternative method with unitCapture like here https://www.youtube.com/watch?v=OAx9HvFXXwc.

PS Awesome mod, can't wait for inbuilt implementation of helicopter animations!