Yeah that seems like a overall fair idea, the ones who noshowed now can't be trusted later on in the league, so it's best to cut them off. I mean c'mon, a week deadline for 3 stunts
Anyway, I have a suggestion of making a "standings" topic... would make it clear who's where at any time (if this will still be a league system - example):
1. Blah Blah - 1 W 0 L - 9 pts
2. Bleh bleh - 0 W 1 L - 6 pts
...
(one point would equal one vote on one challenge by one judge - if two teams would have the same number of wins, then you'd compare them with their points - also I suggest that you give half of the total possible points (7.5) to teams who won by no-show.)