High Karma = Access to Bounty Board. Can post Bounty contracts on Player Killers and Player Criminals paid out of own pocket, and accept other's Bounties.
Neutral Karma = Can Access Bounty Board or Hit Lists. Can post Bounty Contracts or Hit Contracts on Player Killers and Player Criminals out of own pocket, and accept both.
Low Karma = Can Access Hit List. Can post Hit Contracts on Player Killers and Player Criminals paid out of own pocket, and accept Hit Contracts.
Each player crime would carry a Contract price which would increase the potential contract value of a Bounty or Hit. Once someone claimed pay for a contract equal to the price of a crime, contract eligibility for the crime would be removed. Each crime would expire after one week and would be effected by level and crime severity, so that lower level player criminals would be worth less money than higher level player criminals.
Fulfilling the contract would require that the player accept the contract before killing the target, and only a limited number of contracts could be accepted at a time. Each person would also only be able to post one contract at a time, and would have to cancel a contract to start a new one. Fulfillment of a contract would not be listed as a crime.
Anyway this is possibly a good way to institutionalize world PVP while having world PVP issues self regulated by players. You might be less willing to kill, steal, or greif if you know the entire server might end up after your ear. Also Moderators could put special bounties on players who prove especially bothersome or caused disruption in chat, which I'm sure would make the Moderator's job a little more rewarding.