I can help you Sixbreaker with DW editor.
My suggestion:
First - all surface "RED" units should have EMCON status checked.
Second - too many subs in one point is not too realistic (it is tactical mistake). Let them some random possitions.
Third - playable platforms without human player should be remove as soon as you can (with mission script or trigger) Because AI act very chaotic. Unfortunately "
is current controllable" trigger works only for host so you can't check this in single player game (in SP you are always like host).
My solution:
Last time i used this solution for 15 units. For big MP session, time should be minimum 4 minutes (my experience). I know it looks complicated but it is quite simple.
good luck