Seems reasonable. Perhaps a little less than a week, though - I get the feeling that a full seven days might cause the game to fossilise before completion.
As for catchy titles, I'm afraid I'm at a loss.
That's an excellent idea. I've played about with Twine before, and it certainly appeals to me as a writer; I'm sure there are others in this forum that would feel the same way. I could certainly see a contest arising from it, although I'm not sure what else we could do with it that would involve the community. Perhaps something could be created by the writing community as a whole... but then again, that would be more easily done via the previously-suggested route of creating a regular CYOA story.