I was thinking about suggesting this a few weeks ago, but I never got around to it.
On a different forum I post on, there is a guild function that is actually really nice.
The thing is, I'm not sure if there is a plugin for OSBot, and if so, I think it'd be best to make people pay in order to create a guild, and pay to expand it (that's how it is on the other site as well)
It's technically $10 to create the guild, $15 to change the guild name after a name has already been selected, $5 for 5 more member slots (default is 10), etc.
This is how it looks when I post:
The stars to the right of my name are from donating, which has always looked cool in my opinion, etc.
Edit:
But that site doesn't offer "ranks" outside of mediators, moderators, trusted members, and admins.