No, no... I meant offloading the active sensor so the stealth ship could fire. Like a spotter or something.
I think it should be possible to create a two-stage missile that can be launched at a waypoint to drop a buoy with an active sensor that can feed targeting data to the stealth ship, though I'm not 100% sure if this works.
While this should be the way to actually make this work in VB6 and on C#, on C# it simply does not. a 2 stage Missile works only if such missile is:
A - Fired against an active target
B - Under the native MFC range
C - The original target is destroyed after targeting and launching
If all the above are met the missile will find a new active target otherwise it will not.
This is the general rule after thousands of tests on 1.9 version and patches. I did not bother with 1.10 onwards because from the posts I have been reading it was obvious that the problem was not either sorted or even investigated.
So in light of that, I haven't tried the solution Nuclear is proposing but I can tell you 2 things. The active buoy (you can launch them at Waypoints without issues) will 100% function and if you are under MFC range you will successfully fire the missile as well, however, such buoy will be in your game forever as there is no option atm to remove buoys like in VB6. So unless the enemy shot it down you will soon end up with a very cluttered map.
EDIT: if the above for whatever reason will not work, please report it as a bug.