I would recommend that the Merriweather organizers not accept previously published stories.
In a perfect world, this would sound like an ideal situation. Unfortunately, it probably won't work in this instance and would end up being a lose-lose situation for both the author and the various awards offered.
Most authors, when writing a story, are generally eager to get their opus out onto the various boards or to the archive, and have never had any reason to NOT post their stories somewhere. Indeed, one of the qualifications to be eligible for the Kerth awards, which up until this point were the only awards offered, were to have the story posted somewhere. If the Merriwether awards were to be restricted to stories that have never been published anywhere, then they would be limiting themselves to the scraps left on peoples' hard drives, or to stories that could be whipped up in the future. They would also be putting themselves in direct competition with the Kerths - to post a story or not would depend on what set of awards that the author would rather submit to. I think both the Merriweather Committee and the KComm would want to avoid such conflicts.
The more I think about it, the more I believe that complete anonymity of the stories isn't necessarily a must, especially when the entrants are demanding less than complete anonymity of the people judging them. It could be that a judge reads a story and says to themself, "yeah, I think I've read this before." Would that type of casual familiarity color their judging of, say, the characterization of the story? Would it change the physical mechanics of how the story was written? There are stories out there that could be considered very recognizable or unique, but again, how does recognition of the story affect how its put together? If a story is one that the judges have discussed with each other outside the awards, perhaps the judges involved should either disqualify themselves or disqualify the story. Just a thought.
AnnN.
