First, a PbP is a play-by-post - a forum-run RPG, similar to a PBeM (play-by e-mail) but, in my opinion, with significant advantages.

The idea came to me from a Werewolf the Forsaken supplement, Blasphemies (WW30303) and was later solidified when I was reading the "apparent" problems of Vampire the Requiem's horror (http://forum.rpg.net/showthread.php?t=279412).  Blasphemies contained a lodge (similar to d20's prestige class) that a werewolf could join called Lodge of the Crossroads, but the initiation was a solo event.  The text even went so far as to explain that if multiple werewolves participated in the initiation usually they all died.  Then in the forum thread complaining about VtR's horror problem it seemed to me that experiencing the personal horror became very challenging for a group of vampires.  Both, it seemed, needed a solo-type play where one PC explores those themes.

But, I don't like one-on-one role-playing...especially in electronic format.

My idea was to create a PbP with key PCs, but many of the PCs would play characters that were normally GM-run NPCs...possibly even antagonists. The set up would be as follows:
A) Post an [Interest] thread explaining how the PbP would be played along with the basic theme.  The thread would contain general key parts (examples below) that players could choose.
B) A player contacts me and chooses to play a specific PC.  I discuss the basic role of this character in the story, and we brainstorm the exact motivations, knowledges, etc. of this character.
C) Once all PCs have been accounted for I make sure that when to PCs are placed in a room, stuff will happen without a heavy-handed GM (going for an ultra-light touch).
D) The story progresses as the scees between the PCs complete.

Example PCs:
1) The main character.  The story would revolve around this PC.  He would be in almost every scene and would probably have the least "inside" knowledge as to what the story would be about. Unlike most of the other PCs, this character would hopefully have some sort of growth or experience.
2) The mentor.  Kind of a guide so that the main character is not floundering around.  Will probably be more powerful than the main character, but the story is not about the mentor.  Will assuredly not be in every scene the main character is in.
3) The problem.  Not necessarily the antagonist, but close to one.  The main character and the problem will probably butt heads, and my job when discussing with the players on the creation of their character is to make sure the dominos fall.  Where they will land, I don't want to know.
4) The background.  A character full of story.  Not necessarily a mover or shaker, but someone that makes things interesting.
5) A wildcard.  A lurker at the edges.  May side-track the main character, or may be very helpful.  I want this because I don't want to choose the template for every PC, and people come up with very interesting ideas that I would never have thought of.

The Problems:
Moving the story.  The PCs are mostly in control of the scenes.  I may set up the scene and add a few extra NPCs, but the conversations and actions of the PCs will move the story.  If they don't move the scene, it becomes my problem.
Keeping it interesting.  I will do my best to make sure that the motivations of each PC conflicts or coincides with the other PCs so that when they meet things will happen.  I am hoping they won't just stand there and say "Hello, balmy day, yeah."
Others I haven't thought of. Possibly many.

The Goals
Primary: To create a meaningful story (not a chronicle or campaign) where the players explore through their characters a specific theme or setting in a "main-stream" role-playing game that cannot usually be explored in the usual PC-party setting.
Secondary: To allow players to play a character that is usually a GM-run NPC, without all the extra baggage of being a GM, therefore concentrating solely on playing that one NPC with motivations, experiences, etc.
Tertiary: To create a PbP style that has a definite ending (i.e., does not fizzle like so many), but will create a memorable experience.

I tried to be as specific as possible.  The help I need is to identify pitfalls of this style of PbP and any advantages I should amplify.  I will try and answer any questions posed or explain more if needed.

So, no ideas, comments, words of warning, requirements, etc.?

You posted during GenCon. Be patient. We'll catch up.

As a general point to everyone, I understand being eager for responses, especially when you've worked really hard on an intelligent post, such as this one. But please don't bump it up with "where's my replies" posts. It puts people off, as well it should.

That said, hey GenCon people! Quit fondling one another's prostates in the Convention forum and get your minds up into this one, where they're needed.

Best, Ron