Actually the devs encourage taking ideas from other games lostprophet. Even if someone doesn\'t suggest a modifcation with the idea, posting it allows others to do so. Case in point...
I like this idea a lot, the part about the murderer marking anyway. Cept I think that anyone marked as a murderer would be attacked by uber-guards anywhere in the vicinity of a town or otherwise civil area. However, the guards don\'t kill the person, but rather capture them and give out a sentence based on who they killed and what they did after killing the person (like looting I guess). This could be penalties of items, possibly returned to the person who was killed, monetary deductions, and penalties of stats (which in a skill based system would be worse than death). So basically a PK\'er would have to be a fool to head anywhere near a town if they kill anyone, and the effect is the PK\'er could no longer get supplies, equipment, or rest in a safe area.
Additionally a bounty could be placed on a PK\'ers head, and if someone attacked a player with a bounty on them, they would only have to severely weaken the player to capture and turn them in (so the PK\'er would be at a disadvantage in combat). However a PK\'ers rap sheet does not increase if someone initiates combat against them, but no one can be charged for attacking them. I think ultimately free PK should be allowed, since just as you are free to live the game as a non-combatant, you are should also be free to attack anyone you wish. But doing so would have severe penalties that would highly discourage it.
Of course this shouldn\'t be implemented until it is worked to a point that prevents a PK\'er from having any loopholes where they can survive for a time and kill masses of people. And so rather that is an idea for the future, and I think in the meantime the game should have arena based and otherwise consensual PvP, but no free PK, which is what the devs intend to do I believe.