i think some of the postees are missing the point of this being required for an addon.
To create an array of all players, you could
a) tie your addon to require CoC_Ns and use its internal system to create an array of players (peers)
b) utilise a trigger named "My_Trigger" have your addon run a checking script to see if "My_Trigger" is present and if not throw up an error message explaining to the mission maker what is required
For an addon, ideally it needs to be self sufficient requiring little if any input from a mission maker
I see a problem with the apache issue, what if an addon version of an apache is used
Is there really a reason why you need an array of players, could you not use
?(local player) && (driver _veh == player):
An empty vehicle returns side civilian, maybe that could be used in your scripting system.
some mods such as wgl have entries in the init fields of all units, within the config that are used to automatically create an array of units.
Having no idea what your script does, it would seem you have many barriers to overcome to make a truly mp compoatinble addon
What you could do is inherit your own apache class from a bis class and use the init field of your new helicopter class to run the rquired apache scripts
There are so many avenues that could be used, but without knowing what end product you are trying to achieve makes it difficult to answer