Saeviomagy
Adventurer
I think you may have missed the point. Suppose you have the rule "mutual consent" makes someone an enemy/ally. A power says "+2 damage for every enemy in the area of effect" (there are powers which do this), then it would obviously be advantageous to have the guys on your side that happen to be in the AoE decide they are your "enemy" for this purpose.
Only if you are an idiot. WOOT! I did +2 damage to my foes because I hit my ally with the full force of a spell that would have otherwise left him unscathed!
If you're stupidly allowing someone to be an ally for SOME parts of a power and an enemy for other parts of the same power, then no wonder you've got problems.