To be perfectly honest, I’ve done the formal prospectus thing less often than I’ve just verbally described different campaigns I’d be willing to run and discussed them with prospective players, often coming up with variations on initial ideas or entirely new ones during conversations about what to play next.
Ordinarily, my players are my friends and while it’s never happened that all of my friends who play RPGs have been in the same campaign, all of us occasionally have conversations about campaigns and if we come up with an idea we like, I’ll check who’d like to play it and has enough free time to commit to the schedule we agree on.
Even more often, players will ask if we can play a campaign about X or Y, and in case that X or Y does not appeal to me enough, I will say that the concept is not something I am enthusiastic enough about to run a campaign in it, but if they were to run a campaign like that, I’d be willing to be a player in it, help with rules mechanics and campaign preparation as needed, or both.
Agreeing to GM a campaign is a huge commitment of time and attention. I wouldn’t do it for any concept which did not appeal to me enough for me to enjoy the research, writing and creative work associated with it. In comparison, being a player requires much less time and effort, so I might agree to play in a campaign just to support a friend who really wants such a campaign and is going to try running it.
I have proposed a campaign to play with a friend, who agreed to play in it. Because we’re in different countries, we’re going to play it over Discord. Someone on Discord noticed our conversation about the upcoming campaign and asked if they could play. We said yes. Now that the game was no longer a sole protagonist campaign, I asked other online people if they also wanted to play.
Playing online is not, technically, new for me, as I’ve had friends who lived abroad for a few years turn up as a face on a tablet at the table through Skype in our regular campaign, which continued while they were away and once they came back. Playing online with strangers is new and we’ll see how it goes.