I know what this has to do with
Don't make it a Switch trigger - a simple None should work fine. The waypoint will then wait for the conditions to be fulfilled and then move on to the next one. The disadvantage is that, in Cadet mode, the waypoint will show as "Waiting for Others" (which is true to a certain extent) rather than "Destroy".
You could try putting two triggers close together in the area in question. Make the first one Destroy, so that the player knows he has to find targets in that area. Once nearby vehicles have been wiped out, it should permit the player to move on to the second. For simplicity's sake, make that Destroy also and sync it to the trigger.
From the player's point of view, he's told to fly somewhere and destroy enemies in that area. Once accomplished, he has to wait for C1 - C5 to board their heli. Then he can fly home and get out.
Furthermore, the trigger condition will need reviewing in case one of them is killed. I suggest:
(count crew heli) == ({alive _x} count units bunch) + 2