My friends in the gaming group have suggested that I start preparing another Sword and Sorcery Megadungeon. The idea is that this would be a "backpocket" game, which I could pull out and GM whenever we don't have enough players for whatever the main game is at the time.
Backpocket game is a game that I can run with minimal session preparation, and with a small, un-fixed cast. A megadungeon would in theory be perfect for this: 1) There is minimal story besides the experiences the players had in previous sessions; 2) the characters are disposable, and (in the case of the Sword and Sorcery system) can be done very quickly; 3) we can fill in the player gaps with retainers.
In practice, the last time I tried this it didn't go that well -- it was very hard to resist the temptation of chaining sessions together, and running roleplay focused games. Soon, players were getting attached to their characters, and the idea of the characters being disposable, or playing without some characters being around became less appealing.
To avoid that, this time I will try to lay heavier house rules to avoid "town game" and adventures exceeding sessions. The main idea is to force players to flee the dungeon at the end of every session, and have a penalty table to roll for those groups that didn't make it in time. You returned to town, with monsters in tow, in your last hit point, and having dropped almost all your gold pieces, but you did return to town.
Also, I am making the dungeon more mystical and "fun-house"-y this time, borrowing heavily from Etrian Odyssey -- this should encourage the players to see the game more mechanically. I hope!