Okay hows this, instead of points scoring, we have a thing like in Smash the Stack you get to add your tag or mini deface to a webpage for each mission?
For example w00t i have completed basic level 5 then it says would you like to add your tag then you type it in and it appears on the level 5 tag page.
Obviously we would have to protect against XSS but it would be fairly easy to implement