Best to have a good premise at least, that grabs people's interest. And it sounds as if you already have something in mind.
Not really. I just want to write but tend to run into the same 3 problems. 1) Players want to be led by the SC and resist any attempt by other players to interact, 2) the SC is so rigid in their plot idea that the players can't interact or 3) a story gets moving along and the SC disappears.
Like you said, most people won't read the concept when they sign up for something, but maybe if the idea were presented on the forums then the people who do actually read stuff might see it and say, "Hey, I'd be willing to try something like that." Genre/premise/whatever can be agreed on when interest is shown.