We've done a bit of troupe-based play, but usually, there was a main DM.
In our three, hopefully soon four AM campaigns, only the first has been somewhat troupe-based, since we've been three (on five) to DM it.
The next have been mastered only by one person (my brother, used to browse these forums under the name of Aloysius, also the main GM of the first campaign), but created with AM's troupe play in mind (thus, with a GM PC/NPC).
The third, mastered by myself, was not intended for troupe play -- a very ambitious campaign were the players have only one character; they start as apprentices, and they slowly discover the secrets and weirdness of a very old, very mighty Autumn Covenant falling into winter. I planned for the Covenant to be destroyed about 5 years after the characters succeeded in their gauntlets, meanwhile various plots, minor and major, life-threatening and hardly relevant, unfold and they'll have a chance of allowing the covenant to survive Winter. Meanwhile, they can also explore the castle and its caves -- several lives would not be enough, because the whole friggin' covenant is in a regio! There are several layers, the covenant is in 4 spacial dimensions! Lots of parts are forgotten, still haunted by magi thought by the rest of the Hermetic society to be dead, or territories contested by faeries. Between being a "dungeon" that would give headaches to Halaster; the long, rich, and often sordid or tragic history; countless political intrigues; and the slow work of revenge of a powerful demon -- it's the last time in several years I'll make a campaign so ambitious and hard to master.
But the premise made it impossible for troupe play, as I had to have complete control over all NPCs and plots.
The soon-to-start campaign will be mastered by a friend, but she needs to end her write-up of the world, since she doesn't want to use mythical Europe. (Neither did I, but I kept a "parallel world" approach, so that it was still the same countries, language, and rough approximative history). She seems to be wanting to do something a bit akin to what I did, hopefully on a smaller scale!