I am only a reader of the Games, but anyway, to share my opinion.
I rather like the idea of three teams, though I lack any ideas for the way they should be named.
On the anonymity issue. I didn't mind the fact that the posting was non-anon, but the truth is I did react to the names of the authors. I generally try to read based on warnings and summaries but I've ventured into unknown lands only because the author is someone I've good impressions from.
And this is my reason to think anon posting might have some pros.
On the matter of collaboration. I really think in the end it might prove more straining than rewarding. Especially if for some reason the author and the artist turn out to fit well.
After all the artists round of 2007 produced a lot of illustrations for fictions the artists liked (meaning they had impressions and previous affections towards the work they illustrated) and I think as long as the options in the future provide for that it will happen again.
On the matter of length. I personally have a thing for long plotty fics and I would prefer if the authors had the freedom to write as long as they feel their idea needs to be completely developed. I have read a whole lot very good short fics, but in the end I love fics that let me drown in the atmosphere and live with the story and the characters for longer.
And if you do decide to make it a collaboration after all, I think that there shouldn't be strict rule of a picture for every xxxx words. Maybe there should be some minimum, like at least two pictures per fic, but leave the author and artist decide the final balance that would present their collab in the best light.
Finally, the awards for comments. Maybe you should leave that on hold, till you see how it works out in the hd_worldcup. Then you can actually make a decision having more information.
Well, here's my piece of mind and I hope it is useful.