A easy solution will be, to indiquate what type of key it is in parenthesis so the player can bind it manualy.
In my case because i have rebinded all the necessary key, clearing all the key. And i haven't the uttility of the multiplayer key. In this mission, where i needed to choose between 1,2 of course it doesn't worked, thent after a moment i understoot that a default key was binder with 1,2 but i didn't know witch key is in default for 1,2. I then needed to change pilot take the default key and rebind.
It's a little details, but it can block a player in the mision.