You shouldn't be able to plunder players outside a certain BP/level threshold obviously because it's completely unbalanced and unfair for the weaker opponent, doesn't matter if he can ask for assistance from his fellow stronger guild maters. For example why should I be allowed to steal a 12k bp player's coupons and fatten my pockets with 50 for it while he's over there left with only 17 cps crying in the corner. Can you blame me tho, it's freaking 50 per successful plunder...