This is an idea that has festered and gestated over the years, and seems to be coming into focus. I tried something akin to this in Seattle By Night, but there is much more to add.
We often are able to develop a great idea or two, but others can add so much more. Collaborative GMing can work, but its also a strange hassle. Its also not always possible to game with those who you would most like to do so. Even when you have hand-picked a group, commitment and attendance are not always ideal. Multi-tiered gaming is an attempt to get as many of these issues solved as possible. Its a framework which can be used to run many types of games.
The goal of multi-tiered gaming is to introduce differing levels of commitment for players, and thus allow lots of different people to contribute to and enjoy an excellent campaign. It is also ideal for meeting new players, introducing novices to gaming and connecting with former players who have moved.
There are two types of players in this kind of game: attending and remote. Each of these player types has multiple subgroups within it. The GM interacts with everyone, but other than that it is possible that some players will not even know the existence of some other players.
These players come to the location where the game is held either regularly or occasionally. It might be possible to transition from one type to the other if the situation warranted.
These players are the 'stars' of the production. The story is about them. A session does not occur if all of the stars cannot attend. These players are the most dedicated members of the cast. In general there are relatively few of these in the cast.
Why Be A Main Attraction?
Your character is a protagonist whose decisions shape the plot. He will grow and change, gain experience, and make his mark on the game world.
Why Be Something Else?
It is a large time commitment, the other players are counting on you to be here because if you arent the game is canceled. There is not a lot of variety. Some sessions will be less exciting.
The supporting cast are important NPCs for that session. A deadline is set (maybe as late as the same day) where a potential player may express interest in playing. He then informs the GM and gets whatever info is necessary for that session. These characters are always of high importance to the plot for that session. The power level can vary wildly, so people can play very high level and/or powerful NPCs.
As a supporting cast member, a player will be able to experience many exciting roles in the game. They will also invariably gain access to information they would not know from one character to another. Players must pledge to be strict about restricting player knowledge. They must also think carefully about the role of each character from week to week, and commit themselves to the story.
Why Be Supporting Cast?
Lots of freedom and flexibility. Each time you choose to be a part of the game you will play an important NPC who is integral to that weeks plot. You will have an excellent opportunity to influence not only the plot but the main attractions as well.
Why Be Something Else
There is less attachment to an individual character. Its easy to get attached to a particular NPC to then see them die or move on. It requires the ability to keep secrets from not only others but also yourself.
Remote players by definition do not come to the game on game day. They can have either a low or moderate level of commitment to the game depending on their own choices. Remote players have an opportunity to either play the game like a player or GM depending on their choices.
As an organization, a remote player takes on the role of a large group of NPCs and directs their actions. They may communicate with the GM as often as necessary during the week, but their actual instructions must be limited to one page to prevent micromanagement and keep things flexible for the GM. If their organization is at odds with the PCs they can attack them directly or indirectly. Deviousness is encouraged.
As an antagonist a remote player takes on the role of a single important NPC. This character has extensive sway and influence on the game world and is generally equivalent to a main attraction, but on the other side of the fence. Any amount of communication with the GM or even a PC (with permission) is allowed. Weekly instructions are limited to two pages. In crucial times, if space permits, this player may be invited to be a supporting cast member for that week.