As a paladin or other good aligned character, I would like to see a mechanic that would allow you to bring evil doers to justice by non lethal means. There should be a way to subdue (bring to zero hit points) without killing your opponent. When an opponent reaches zero hit points you could get an option to subdue or deliver a coup de grace. By this means good aligned characters may be able to collect bounties by "arresting" the subdued opponent. How this mechanic would exactly work within the scope of an MMO I don't know, but it's something to think about.