Currently if I wanted to create, what appears from the sky as a large land battle, one of the ways I could do that is place numerous dozens of units in combat, enough so that by the time the player takes off, and makes it to the war zone there are still enough units left to simulate this battle.
If we had an AI re-spawn option, I could place 1/4 of the units near each other on perpetual re-spawn and from the sky it would appear as a large battle without having to fiddle with the current time consuming work arounds, or adding a ton of units so enough survive.