Here I describe a possible system. You would get an npc in important hot-spot places for PvP So maybe in Varrock or Falador near a safespot on the RS gold outskirts of town or in the bank.
The bounties needs to be of a player that is within a certain number of combat levels as you. For instance a level 100 character cant maintain level 20 combat duties. Thats just genocide! Also the bounties are random, so if you take one you must meet it or wait 20 minutes to get a different one. A bounty is never lost, if a person does not do it in a day's time then it is put back into the huge bin of bounties. Or when you trade one off, which means that your 50k that's down "Blackxp" for instance is never wasted and he will die at some point.
You also can just put a bounty on a participant every 20 minutes, which means you cant try and RWT it by putting it on a player constantly and with a buddy reap the benefits. (you will never receive a bounty you put yourself) This may donate to The Camping system. Members of your camp who have a bounty on thier mind will probably be indicated with an arrow, a large blue one, over thier head.
I've made an idea to position your PvP abilities. I suggest that it's allowed to be ranked on the hiscores system. I thought of this idea to see how you could compare to others with PKing. To have the scoring system, we would have points. These points could depend upon: How many Cheap RuneScape gold players were involved from the kill. A specific point will be given to every one of these variables, and you must have at least 5,000 points to enter the hiscores. I believe this sounds reasonable and it is going to help compare your PvP mini-game scores with other people.