We already have a story going on exactly like that. You could hop over to the Beyond Alpha Centauri discussion thread, and sign up to write for a faction.
Some factions are already taken.
University = me
Hive = Frankychan
Earth Coalition = Kassopeia
Drones / Firaxis = Mr. President
Sparta = Sprayber
Protectorate of Man = Lonestar
Believers = Silence
Morgan / Peacekeepers = History Guy
Cadre = GeneralTactius
Cult of Planet
some others I forgot
Feel free to sign up and write! We could always use another author