OK - this may sound complicated but it's an idea...
Would it be useful to be able to "group" groups? I'm just thinking about big boards here, where it may be the case that 30+ membergroups could exist. For example, here we have many staff groups (Developers, Support, Documentation), and every staff member may also be part of a bigger groups called "Team".
So, if you wanted all your team to have access to a board, currently you would have to check every group in your "team", or everytime you add a new "team" member add them as a member of team as well as,say, a developer.
What if you could create a group called "Team", and instead of assigning members to it, assign groups to it. This would probably be achieved by an additional field in the membergroups table, which could list, say, 20 id's.
This means that whenever anyone is assigned to, say, developer, they are immediatly assigned to "team" too. How useful this could be outside permissions I do not know, but I thought it was worth a mention. The problem may be code effeciency getting these extra group numbers - probably not possible then but oh well *ramble*
I like the sound of this idea, would go well with clan forums too, as most have groups for command staff, members, divisions, jobs and all that fun stuff.
I would use it for sure - I'm already thinking of ways I could streamline my groups with that.