Why not have them actually start combat with each other?
Set them to a custom faction, mark it with special combat. Reduce their hand2hand to zero and they won't even be able to hurt each other.
Cheers, but I'm not sure that would really work, since they only fight for a few hours then go back to normal (i.e. its a fight club, they're not actually fighting because they dislike each other. Perhaps with some scripting I could make them temporaily be put in a faction then removed at the end. But that could get quite complex.
By the way, it seems there are problems with just basic changes in AI packages when related to using AI simulated combat. For example once i've console 'resurrected' them and they start doing it properly, once that package is over and they are supposed to move to the side a do a cheering package, they just keep fighting, once again, I need to 'resurrect' them to get them to do the correct thing.
Also it seems like when left normally, they barely ever do the animations, they just stand there doing nothing.