Yeah... always an issue. Metagaming is the very bane of my existence. Doesn't mean I'm not willing to try, somewhat. And probably watch it fall apart. Unfortunately these psychological things are my favourite things to do in terms of roleplay. Why am I like this? Oh well.
In retrospect, I can see how my post comes across as "Your dream sucks", which is bad, so I apologize for that. Good for you for not letting it get you down. I do think this will be a challenging project, but that doesn't mean it can't, let alone shouldn't, be done. I doubt this type of game has never been done before, but I can say that I haven't seen it done in my 6+ years of online roleplaying. I think there is a case that that uniqueness is very much a justification for pushing through with this concept.
I guess the next thing to consider then is what the appeal of this project will be. In a lot of what your idea appeared to be to me at first glance was a murder mystery, which, as I said in my first post, is a different beast in this type of roleplaying environment than it is in a short story or novella. The primary difference that I believe will potentially cause problems is that of perspective. One of the means by which mystery novels typically maintain the suspense for the reader is by limiting the perspective from which the reader is being exposed to the story is through the point of view of somebody who doesn't know everything that is going on, and therefore as the protagonist is learning information, so is the reader. At least for me, it is this suspense and desire to discover the mystery that makes reading these types of stories appealing.
So going back to collaborative roleplaying and metagaming... In my experience, the nature of participating in the kind of activity we do on this site is that we read what others are writing, and then we feed off of that creative energy to produce our own writing in the worlds that we are more of less creating together. Metagaming is basically an extension of this very activity; writing based off of information that others have posted. Discernment can and should be employed to determine what our given characters should realistically know and be able to observe, but I can see where the line between good participation and metagaming can be hazy.
All of that to say, while one solution to the metagaming potential problem would be to make rules against it, I suspect that, for me anyway, that writing my character as if they don't know who the murderer is even though I personally know who they are might not be as fun for me. I would lack the suspense of striving to figure out who the culprit is and instead I would be struggling to find a balance between writing my character discovering and processing clues and writing my character coming to conclusions that they shouldn't have even though I personally have. As such, in my opinion, I think the game would be most entertaining if there was a way to keep us players in the dark about the identity of the murderer, and perhaps the GM could play the kind of head games with us players that our characters are also experiencing.