Yora
Legend
I am getting increasingly serious about starting a West Marches campaign. My experience with my Isle of Dread online campaign last year makes me feel that I could quite well end up with more than 10 players, and get the demand to have a second or third GM run at least occasional adventures in the same game world. While I don't have any experience with this, I know enough about such campaign to see that there are numerous things with which you could make things really more difficult for yourself. 
The idea for this thread is to discuss how to avoid doing that.
To quickly pin down the basic parameters of this campaign style, the basic idea is that you have a pool of player, who each can have multiple characters of different level, who form regularly changing, temporary adventuring parties to set out into a wilderness for a limited scope exploration adventure.
There are various reasons to run such a campaign and play in it. One of the most attractive aspects is that it allows for frequent play without a fixed schedule. Even if you find a day every week or every two weeks that usually works for all players; when you have six people, one person being unavailable can become a very frequent thing. Open table games in general and West Marches campaigns specifically use adventure structures that don't require regular attendence and are not disrupted by players being absent. It does of course come with limitations for what kind of adventures are possible. The adventures have to exist independent from specific PCs, and getting involved in ongoing events in the game world becomes impractical. It more or less limits adventures to the exploring of ruins and caves, or the hunting of monsters or searching for treasures. This is one of the reasons why the West Marches concept generally excludes town adventures.
Adventures of this type are not what everyone is looking for in a campaign. But this is something that comes with the subject. It's not a universal solution to handling large player groups. It's one for campaigns of serial one-shots, with everything this brings with it.
While campaigns like this don't have to be limited to D&D and retroclones, I think most solutions that apply to any specific edition also translate very well to all the other, since the basic dice mechanics are basically the same, so I am putting this in this forum.
I already mentioned one method to help with making such a campaign work, which I simply asserted without elaborating on it. I think such a campaign should encourage players, at least those who play more regularly, to have multiple characters that they can switch between. When you have the party composition change in each adventure, you can end up with parties that have characters with overlapping specializations, while other skill sets are completely absent. Or you can have characters of widely different levels. By having players have two or more characters of different classes and levels, any group of players that has come together to play has much more options for putting together a good party.
Building on that, I also have a second recommendation: Systems with faster character creation and fewer abilities provide big advantages in a campaign like this. You could of course make a West Marches campaign in 3rd edition or Pathfinder, and I believe the original West Marches campaign actually did that. But there are two issues that become more pronounced with such rules systems. The first one is that the creation of a new character needs more time reserved for it. With a very simple edition like BECMI or OSE, you can easily say at the start of an adventure "give me a minute, I quickly make a new thief if none of us have one, and then we're ready to go". And while I understand I am making a completely subjective claim with this, I also think having more bare bones character sheets helps players not getting too attached to specific characters. I know, but hold your outrage! If the planning and expanding of a single character becomes more complex and work intensive, advancing that character becomes a more serious undertaking. I see this as a disincentive to switch between characters, as you have big plans for how you want to advance your main character. I see the West Marches campaign concept more as a game for players to play with the dungeons, than to play with their characters. Treating PCs as somewhat replaceable, and perhaps the campaign as a whole as more casual, should help with a smoother game in my opinion. It does after all not advertise deeply involved stories, but irregular (though not necessarily infrequent) on and off games for three to four hours at a time.
I thinking making the individual adventures in such a campaign pop, when they don't utilize the common modern lures of current adventure styles, is the main topic I want to dive into with this thread. But this has already been a lot of stuff to start chipping away with and I want this to become a discussion for us o learn from, rather than a manifesto of my armchair ponderings.

The idea for this thread is to discuss how to avoid doing that.
To quickly pin down the basic parameters of this campaign style, the basic idea is that you have a pool of player, who each can have multiple characters of different level, who form regularly changing, temporary adventuring parties to set out into a wilderness for a limited scope exploration adventure.
There are various reasons to run such a campaign and play in it. One of the most attractive aspects is that it allows for frequent play without a fixed schedule. Even if you find a day every week or every two weeks that usually works for all players; when you have six people, one person being unavailable can become a very frequent thing. Open table games in general and West Marches campaigns specifically use adventure structures that don't require regular attendence and are not disrupted by players being absent. It does of course come with limitations for what kind of adventures are possible. The adventures have to exist independent from specific PCs, and getting involved in ongoing events in the game world becomes impractical. It more or less limits adventures to the exploring of ruins and caves, or the hunting of monsters or searching for treasures. This is one of the reasons why the West Marches concept generally excludes town adventures.
Adventures of this type are not what everyone is looking for in a campaign. But this is something that comes with the subject. It's not a universal solution to handling large player groups. It's one for campaigns of serial one-shots, with everything this brings with it.
While campaigns like this don't have to be limited to D&D and retroclones, I think most solutions that apply to any specific edition also translate very well to all the other, since the basic dice mechanics are basically the same, so I am putting this in this forum.
I already mentioned one method to help with making such a campaign work, which I simply asserted without elaborating on it. I think such a campaign should encourage players, at least those who play more regularly, to have multiple characters that they can switch between. When you have the party composition change in each adventure, you can end up with parties that have characters with overlapping specializations, while other skill sets are completely absent. Or you can have characters of widely different levels. By having players have two or more characters of different classes and levels, any group of players that has come together to play has much more options for putting together a good party.
Building on that, I also have a second recommendation: Systems with faster character creation and fewer abilities provide big advantages in a campaign like this. You could of course make a West Marches campaign in 3rd edition or Pathfinder, and I believe the original West Marches campaign actually did that. But there are two issues that become more pronounced with such rules systems. The first one is that the creation of a new character needs more time reserved for it. With a very simple edition like BECMI or OSE, you can easily say at the start of an adventure "give me a minute, I quickly make a new thief if none of us have one, and then we're ready to go". And while I understand I am making a completely subjective claim with this, I also think having more bare bones character sheets helps players not getting too attached to specific characters. I know, but hold your outrage! If the planning and expanding of a single character becomes more complex and work intensive, advancing that character becomes a more serious undertaking. I see this as a disincentive to switch between characters, as you have big plans for how you want to advance your main character. I see the West Marches campaign concept more as a game for players to play with the dungeons, than to play with their characters. Treating PCs as somewhat replaceable, and perhaps the campaign as a whole as more casual, should help with a smoother game in my opinion. It does after all not advertise deeply involved stories, but irregular (though not necessarily infrequent) on and off games for three to four hours at a time.
I thinking making the individual adventures in such a campaign pop, when they don't utilize the common modern lures of current adventure styles, is the main topic I want to dive into with this thread. But this has already been a lot of stuff to start chipping away with and I want this to become a discussion for us o learn from, rather than a manifesto of my armchair ponderings.