This sounds very tough to pull off to me. You could try making the AI units owned by an existing player and regulate what units that player can control. That would be what I would try first.
Make Neutral Extra treat Neutral Victim as an enemy and vice versa.
Make each team allied to either neutral extra or neutral victim and an enemy to the other.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.