If that were the case then unless it was a known universe then someone might write a story defining the universe and the others would write off of that initial story. Those which became published could be drawn on for source material for stories as yet unfininshed until all was completed. In order for it to work together, it would be necessary to stay within the universe's guidelines and true to all of the story thus far written. If something this structured were offered as the contest then a not so structured alternate could be an option. That way even if the writer thought she had followed the rules of the contest and it was decided in some way that it had not then that story could be omitted from the shared story cannon and entered into the general contest.

Lots of good ideas for this and I can't wait to see what is decided.

All my hopes,
Sasha