Some suggestions for structuring eposidic games ...
Create an organization where the PCs are a few of the adventuring types on the payroll. New players will be PCs that were formerly faceless NPCs and missing players can have their characters called off for "more pressing business."
Be part of an organization where the adventure comes to the PCs:
Military outfit (Complete a mission)
Private Investigators (Serveing clients)
Law Enforcement (Solving crimes, Search and Rescue)
Examples: Who hasn't said that SG-1 is a pitch perfect set up for RPG play?
Be part of a group where the PC are always coming into harms way:
Pirate ship (Storms, law enforcement patrols, backstabbing)
Explorer's Guild (new lands, angry natives, hostile fauna)
Caravan (bandits, haggling, smuggling for extra profit)
Rebels (A more gritty version of the military outfit above)
Example: "Our five year mission ..." except that the bridge crew wised up and sent the PC instead of riskig the whole command structure just so they could see things "first hand."
Both examples are from TV shows for the obvious reason that the TV industry has explored every eposidic theme over the last two generations. You know there was a time when "soap opera" plots were only in soap operas. j/k.
My favorite personal invention was to have a spaceship crash land with all the PC (and extras) in sleeper pods. The crash caused a pod lockdown AND damged the sleepers. i.e. New players were those that recently escaped their pods and missing PCs had been hit with "sleeper sickness."
Thanks for the suggestions! I knew I left something out, but I guess I'm also trying to specifically stay away from suggesting how people run their games. But I'm glad you did--story structure is something I might need to cover in a later article.