From a system administration perspective I think this might solve some peoples problems with having multiple groups that run Kara and how or where they sign up. Looking at what Toddler has asked for leads me to an idea for a solution.
Allow each site admin to create Raid Groups in the site. In the group they can define as many or as few people as they want. The account page should have a drop down that allows the admin (or officer) to select the group/s (or none) that a persons account should belong to. On the Character Roster this should open up a group selection box for the character based on the groups that the account belongs to.
The creation of a group should create 2 other features/options for the site.
It should automatically create a thread tag for that group with the associated accounts as members of the tag and allow the admin to designate who can moderate the tag.
It should also create the group within the scheduling system. This would allow the schedulers in a guild with the ability to schedule events for their raid group. A new selection would appear on the event that would allow them to select the group the event was for. Based on permissions or options the event may or not be visible to others. Independent of visibility the event would only allow members of that group to sign up. Some guilds may want all events visible so that they can see every raid for every group. Others might only want the group members to be able to see the events.
Anyway my 2 cents regarding Toddlers requests and others I have seen regarding groups and raids with how BC has structured things.
I was just looking for this exact feature for the same reasons as Toddler, but Saudorun's ideas are great expansions on the concept.