Getting access to multiplayer aircraft is currently not possible with the SimConnect API, the „application programming interface“ introduced with FS X back in the days.
https://docs.flightsimulator.com/html/Programming_Tools/Programming_Tools.htm
Only access to „AI controlled vehicles“ (aircraft and boats…) is given. And to create („spawn“) additional “AI aircraft” (AI = artificial intelligence - or simply said, "controlled by the computer/some algorithm/pre-defined flight path ;)).
What might be possible for a replay tool could be to „merge“ several user captured flights and replay the N - 1 flights as „AI aircraft“ (where N is the number of recorded user flights).