Since a justice system is going in and there will be bounties for those who "earn" them, so to speak, I would like to see a system where players can put bounties on other players.
This can serve several functions, one it can be an excellent gold-sink, make the bounty fee very high to even allow a bounty, then of course allow a player to put whatever reward up they can afford.
Two, this adds to the social feedback in the game if a person becomes an uncivil element within society the player themselves can provide the in game feedback needed to correct anti-social behavior.
Three, the fun factor is through the roof considering we have a real sandbox element now that the players themselves must manage and work through.