For pking, I think points should be based off of how many kills you can get, before you die.
(1st kill) If 1 kill, before death = 1
(2nd kill) Then the next kill is 3 x more = 3
(3rd kill) Next is 2x more = 9
(4th kill) 9 x 3 = 27
(5th kill) 27 x 3 = 81
(6th kill) 81 x 3

Rules

1. They have to get each kill in less than 10 seconds, otherwise you start back at 1 point. (So you won't run away, and camp)

2. Your rule from the quote. (Mob pking punishment)

3. Killing guild members and allies reduces points

This way, it rewards people for skill, and not just grinding and spamming sword.