Maybe something in the ballpark of ero-empire but slower-paced an light on rules.
Easy to get into, not pressing players to make massive write-ups or get things done by a window. A few guidelines should be enough.
You know what? I'll go ahead and make a framework for this, and then maybe we can discuss/refine it a little and then launch it in it's own thread, or several, here's what I'm coming up with.
/erp/ collaborative fiction mini-dictionary
World:
A setting with an individual forum thread. Each world will have it's own themes, be they science fiction, fantasy, or modern. Different worlds are each their own "game" or "session," and can have different rules. The thread starter should generally be seen as the DM of a world, and ideally will help encourage players to join and write, perhaps by coming up with in-game events to act as a writing prompt, or setting the rules for games with competitive elements.
Civilization:
Some group of probably but not exclusively sentient beings. A civilization takes the general scope of an "empire."
Site:
A noteworthy place, can be part of a civilization, or simply just a place that exists in the world.
Entity:
An individual being, be it a citizen of a civilization, a wandering adventurer or merchant, or even a hive-mind that in turn makes it overlap with a civilization.
Relic:
Like a site, but a thing instead of a place. To be worth noting it should be a interesting object, something special and unique within the world. Can overlap with entity, such as a possessed item.
Player:
A person writing for the game. In a step away from the ero-empire format, a player doesn't need to be a full civilization, a player can be an entity, playing as a person visiting the various civilizations, voluntarily or otherwise.
That's all I got for now, I want to add some stuff about declaring something (like an entity, place, or relic) and setting how much other players can interact with it. (like anyone can write this character vs only I may write this character.) But I need more time to mull it over.