I know how to use cs weapons in Multiplayer, it is a very simple fix.  Remember most people do not fly detect crash on.  It is in your realism settings.  If to objects collide they will end thier flight.  Well cs weapons are in fact a flying object.  problem solved.  If you would like to test this out have a friend fly with crash detect on and see what happens.  On another note if both players have csweapons they will also see the incomming missle.  other wise the sys will default to whatever it can match up, i.e. flying helo's.