I have been thinking about this for a few days and I think this is an awesome idea and could possibly help revive the wilderness.  What if you were able to disable receiving XP for Attack, Defense, Strength, Hit-points, Prayer, Ranged, and Magic.  This way if you are training you could disable say Defense XP so that if you accidentally click Defense you don't receive any XP for the kill.  You would only be able to do this for combat skills that raise combat level.

I got this idea because I have heard a lot of people saying they want to make level 33's to have a pk party of only level 33's.  With the ability to lock out xp gained for combat skills this would allow you to make your build, get to level 33 and then lock out all xp for your combat skills which would allow you to stay at level 33 or any level that you wish until you re-enable xp for the skills that you blocked.

Just a crazy idea, that might make for some interesting pking.  Let me know what you guys think!