Hey,
I think pking would really attrack player to the server. It truly is the heart and soul or runescape. My suggestion is not so much to add it, but how to implement it.
Personally, I am not a fan of teleports that take you to dungeons. Therefore, my suggestion would be to turn the dragon cave teleport into an edgeville or varrock teleport. Then using a cave entrance to access the dragon cave rather than having a teleport for it.
I would love to see pking on this server, post if you agree.