Perhaps not for right now, but:

We have a game called Fill the Plothole wherein someone posts a selection of funny or odd fanfic summaries on the Board, and people write short stories based on any of the summaries that strike their fancy, "filling the plothole" of the summary in the process. Usually these end up being humorous, but they don't have to be. You can see examples from previous games here.

It's not a competition and agents aren't involved,* but you could definitely pick all summaries from Potterverse fics if you wanted to start a game sometime.

~Neshomeh

* Usually. People *coughmecough* have used FtP as a platform to write mini faux-missions, but that's not the point of the game. At all.

I'd be interested in doing something like this, however I agree with Phobos' second and third points.

There are some merits to what you are proposing. Encouraging people to write is always fun. We've had writing contests before, with varying degrees of success. So the idea can definitely work. I would just caution you on a couple of things.

First off, being as specific as which fandom to write in might turn people off of the idea. Some people may not like Harry Potter, or they may want to do something else. Widening the focus a little might not be a bad idea.

Secondly, your idea hinges on everyone getting permission, which is unrealistic. There are going to be a few people who just are not ready for it. So, I would again shift the focus to something that doesn't require permission. This will allow everyone to participate.

Thirdly, while you may get some people to participate for writing tips (hS runs a writing challenge that runs on everyone involved giving concrit to at least one other participant), you might have better luck with some other type of incentive.

Really, all of that is logistical. If you can find a way to make it work, then there is no reason not to give it a try.

-Phobos