The thing here, for me, is if he owned up to the whole thing on his own you could say it was a joke, and that he owned up to it once it looked like it was going to far. If he only owned up to it because he got caught then that's a different story.
The entire offense is dead serious. A player's identy was stolen and used to make him look like he was cheating. This, of course, means the offender has cheats. This is not a bad thing in itself, lots of people have cheats for viewing cheating demos, making cheater vids, or for any other novel reasons besides cheating. Using those cheats in bad ways is the problem. And although this is a new twist on things, it is definately a bad way to use the cheats in your possession.
Bottom line:
Did he do the deed as a joke and own up on his own? 6 out of 10 on the serious offense scale.
Did he get caught then own up? 11 out of 10 on the serious offense scale.
Matze, I have nothing against you at all. But as this topic has been put under my nose over and over I have continued to mull it over. In my mind I placed nameless faces in all the positions involved here. In this objective manner I have concluded that this offense, even when viewed as a joke, is one of the holy grail offenses, taking someone else's identity. That in itself is of very poor taste and judgement and should be, alone, punishable. If the fact prove that you were caught and then owned up to the deed then one can only conclude malicious intent. This, I think, is more severe than someone outright cheating in a match.
My recommenation:
If he owned up on his own: 6 months bannishment.
If he got caught then owned up: 12 months bannishment
Don't worry Matze my words above mean nothing. This is just my unbiased opinion. Step outside yourself and look at it. I'm sure you would agree.