Well, if vB is anything like phpBB or IPB, creating some forums for a new group would involve a forum, and a set of sub-forums with restricted permissions. I would hope that vB has some robust usergroup permissions (I can't remember rightly, I should go look), so all you would have to do for usergroups is assign a leader, and let him allow/deny people into the usergroup.
As for the styles, well, a
simple style would be fairly easy if you use CSS. Just some color changes, etc, and walla, a new version of whatever default style we would have.
And then there's the extensive changes you could make with templates, like what all of SWF's groups have. Those take a
long time. If you're just changing colors and a few things like that, making a header, etc, you could do it quick, but if you're doing a complete revamp it takes upwards of a week's worth of afternoons.
So yeah, it would definetly be a lot more labor intensive in that area. I think that the benefits in other areas will outweigh those cons. A simple 'you-can-have-your-group-hosted-on-the-main-board-if-you-wish-after -playing-here-for-three-months-as-an-active-group' rule would help. Although, we don't get as many new groups as we once did.