I don't not (double negative on purpose) like the idea of sub forums for advertising league openings and looking for leagues (would you like one subforum for both or 1 for each?), but I'm not sure it's all that needed. I mean, you could categorize things 10 levels deep, but going through all those levels to get to the content probably wouldn't be worth it. This would only be 1 extra click, but is even that worth it? Is this forum that cluttered that it's difficult to get to the general threads from the advertising? I don't have a position on that either way, myself. I ask to see what the general consensus is.
I don't think the idea of one thread would at all work though as it would be dominated by leagues with active posters. Sure, threads that get lots of posts keep getting bumped to the top, but I think the problem of getting buried would be even worse in one thread. And where do you start reading from? You could read backwards, but that makes comprehension difficult at times. I would kind of like to see each league limit themselves to one thread per season, but I wouldn't want to make that something you have to abide by either.
Unfortunately, I don't think there are all that many strong opinions in this forum much anymore. Hopefully I'll be proven wrong.