In big events like this it might be better to have sign ups and then RNG the team ups. You could offer some groups to form on their own if they wish or others to opt for a roll. Not only does this keep groups in the 3-4 range but it can also open up fresh CR for people who might not otherwise thread together. I know other games use a method similar to this and I think someone else mentioned it already. Then once signups are over you can post the groupings (and maybe let others know if they miss these things they are still welcome to other aspects of plot or something idk).

I'll admit, I was a little confused about sign ups for this event vs. actual game play. I got lost in where my character could be or if a thread was already maxed out or not. I'm not very certain how to clear it up, I'll admit part of it was possibly my own fault for being out of the loop the past two weeks with my own stuff. But I think the above might help with that to some degree.

As for the Wild Pokemon threads. I don't do them quite as often as other people, but the ones I HAVE done have been pretty entertaining. I don't see why they can't continue. Although I do understand how they can be a lot of work for the mods. Maybe there are other ways to keep the mechanic without it being so troublesome? IDK, but I do like that the option is there. It's a unique part of this game that I would miss if it were gone.