It'd be great if there was a button for "moderated" group chat. This would allow officers of a group to say something to the group, but when "moderated" the members of the group cannot chat.
The time this is handy is for groups that are announcements based, like clubs that just need to announce events, groups for product announcements, etc.. but would cut down on the chatter of people cross-advertising, chatting in incorrect windows, etc.