I like the idea, but I think it would be too closely related to slayer, and applying it to other skills would actually reduce the variability of the game, in that each skill is trained differently (with the exception of combat), and by introducing this, it makes all skills trained the same way. Right now we have something like this: Go to slayer master and get task, finish task, do some laps at an agility course, woodcut a bit. Changing it would give us this: Go to slayer master and get task, finish task, go to agility master and get task, finish task, go to woodcutting master, get task, finish task. Hopefully I was able to get my ideas across without too much confusion :P