you can place units owned by a player without an startlocation in the game. they are not preplacable, unless the editor lets you do that.
they dont belong to p12, you can use triggers to move them. BUT you must use the specific player, or else it wont work, like liek say p8 has no start location and you order force 4(say p8 is in there) to move, it wont work.
i dont know if this has been found out but i think it pretty cool! i dont know if this works for extended players.(i dont think you can order extended players around, can you?)
It has, and has been used countless times.
ok then...
but can extended palyers be used?
also i have never seen it used.
It was in the random mapping tips way before you ever posted this.
"Units created for players without start locations, A.K.A "zombie" units, will always be hostile, and unable to be affected with trigger's actions. They will also follow units they attack like a hero unit would."