I play this game called archmage, and if someone attacks you, you have a "Counter" on them which appears on a counter list, which the counter exires in 24 hours. You can attack them once with your "Counter" on them even if they are in protection or offline, an eye for an eye. I think this idea could work for pvp cape. That way the people who want to just do quests and not pvp, won't give out any counters so they can't be attacked.
And the option to turn on/off the cape would be good idea also.
