IP address tracking and Jagex accounts would stop people from Alt account cheating. And would also be able to identify if you're really putting up a fight or not and if you're not then the game will not put out any XP for cheating.
As for players who don't want to risk items they will get a little bit less XP than somebody who is actually risking items. I think that the option would be available for both.
i believe thats different. there are players who will NOT PK no matter what. there are yt videos of players doing all kinds of builds to take down people quickly and thats something the normal player who doesnt do pvp will want to understand.