I like the idea of having a Top PKer list, but there shoudn't be rewards for being on it. Also, make it so that only kills for level 150s every one hour per that person killed.
Ex.: Scylla kills Silence. Gains one kill one the PK list, Scylla kills Silence again ten minutes later, no points are added. An hour after the original kill, Scylla kills Silence one last time and gains another point.
Seems fair t me. Those actively PKing/getting kills/dying will rack up the points faster than those who kill their alts. Just an idea.