I don't know if this has already been suggested, so I'm going to point it out anyways.
As most of you are probably already aware, the maximum number of people in a hub that is not generic is 4. I only ever join/create hubs for Pokémon Diamond, so I'm under the impression that all other game hubs have a similar limit.
So I was thinking that we should increase the maximum number of people to 8 in specific game hubs as well, because sometimes it is tedious getting everybody that you want to talk to into a generic hub. In addition, generic hubs do not show up in the Pokémon Center forum, which is likely the most active part of the site (in terms of hubs).