[Map Editor] Any way to get AI to be "turned off" initially?

I made a map, and I have the AI player guarding specific spots. I don't want the AI to move the units off of those spots, but when the AI builds itself up (i.e. makes villagers and advances through the ages) the new units it makes will be allowed to rush and attack the player.

Is there any way to make the AI "defensive" for the initial units that it spawns with, but allow it to attack with the units it makes itself?

Looking for a (relatively) easy way to do this, I don't know how to do this other than forcing the AI to be defensive through triggers and assigning every single one of the AI's units to a specific area. Which would be tedious, but if there's any other way..?