I just commented on another of your posts but didn't notice the date. I see that this post was from a few years ago but I will respond anyway.
Over the years of creating tournaments, I have started having two kinds of tournaments. I have typical open tournaments where I set a certain rating limit slightly above my own. Over time, I found that inviting some chess friends on here meant I had to increase the rating limit to allow them to play. The problem for me is that it was not very competitive as there wound up being too many players 100 or 200 points better than me, making it hard for me to be competitive.
So, I now have two types of tournaments. The second one is an invitation only tournament for people that I've played before. I increase the ratings range for this tournament, but it is safer because the people who play are only invitees, so there is a limit to the number of stronger players who can join. But I have found this type of tournament to be the kind that you have mentioned and that you've called a "cohort" group. Whereas the open tournament typically has a lot of new faces, the second one is mostly old rivals and it's fun to play as rivalries are developed among players who have gotten to know each other.
As I initially designed my most recent tournament, Zippy Tourney #2, I tried to set it so that 3 out of 4 players would advance in each group. I thought that it might be interesting to see if playing the same players more than twice resulted in finding some "chess friends."
Alas, 1/2 or fewer of the players are allowed to advance in a tournament round. This certainly makes sense for keeping the tournament length within reason. So how might one create a cohort of players who can learn from each other? Perhaps as I continue this series of "Zippy" tournaments, some of the same players will join consecutive tournaments and a cohort will form that way.
Just thought I'd share some of my thinking and solicit advice about how a tournament director might help make this site most beneficial, educational, and fun.
I'm happy to hear your suggestions and experiences. Best of luck and learning to you all. Keep it zippy!
- eyeronic
P.S. You're invited to join us: Zippy Tourney #2 - 16 Under 1600 Players Become Chess Friends