the punishment idea works the same like the modding - only people who agree to it should play this game, but there would always be someone, who didn't read the rules.. and someone who didn't got rewarded due to it. It wouldn't work that good...
So in the end, it would probably just stay with the 4 fun. (but it could work due writing the reward/punishment under the own guess for the above avatar. as the example .. my aboves avatar is "random guy" and then under it, I write > reward for the next... free mod for 1 map, punishment for a false .. blah. So the poster would directly know what he is going for and would have to do maybe. Lucky persons will have 2 wishes "rewards from above, punishment from .. I don't know the opposit .. poor english.)
In the case, someone won't fulfill the the reward or punishment, the post will just be ignored, so the before poster will edit behind the wish/punishment if they are done already and first if that doesn't happen in a close timezone, someone could quote that post and reanswer to it... (in the case, it happens like this, the first answer was wrong anyways... why should someone refuse a reward =p )
"I am pretty tired and probably have to edit my post again, because it could make no sense atm"