Could you not do something like:
"Are rogue troops present?
If yes, check to see if there would be a battle between any opposing realms were the rogue troops not present.
If yes, the rogue troops stand aside.
If no, the rogue troops attack/defend/whatever."
I feel this particular feature adds nothing to the game beyond frustration and the occasional, "Oh, cool, look, the undead are fighting with us".
