Within ArcGIS Online, it would be great if I could add a group as a member of an existing group. This way I could create role groups for each work group in my organization and then mix and match them easily for specific projects. It would also make collaborating with other organizations easier. Rather than adding all the users from a neighboring county that we are collaborating with in to a group so they can see maps/data in my organization, if I could just make one of their groups a member of one of mine, it would be so much simpler. IN addition, myself and the administrator of the other organization could more easily add and remove people across each others subscriptions.
