The fundamental point in this problem is, who is detecting the enemy? If it is a friendly soldier, then a guard waypoint is appropriate. If it is a trigger, then guard waypoints are no good.
You don't need a script. However, what you do need is to make the triggers switch triggers. Put move, S&D and cycle waypoints in each of the trigger areas. Each trigger should be synchroed to the move waypoint in its own area.