I'm not too keen on this idea. Mainly because Pokémon Universe is meant to reflect the console games. In the console games - there aren't any guilds etc.
Pokemon Universe is meant to reflect the nostalgia, and the joy, that all players had when opening up and playing their first Pokemon game. We are the joy you had at getting your first starter; at defeating your first trainer; the sadness of losing your first gym fight; the constant challenge to beat everyone around you, including your rival.
We represent the ideal of Pokemon, not the game itself.
At least to me. So, there will be guilds. And anything else we decide to put in to, plainly, make the game more fun. We're not out to mimic the original games. We're here to make them more fun, while keeping what we fell in love with.
EDIT: Speaking as someone who runs his own guild on WoW, unless you are running end game content, or their is a fight between guild members, guilds require absolutely no effort to maintain. You start it, invite people, and that's all.
Nothing will be fundamentally different in PU. Unless you make it complicated, it will be the same as maintaining a large party of friends you enjoy talking to. Things are only as complicated s you make them.