It would be useful to have the ability to add a group as a member of another group. This would allow us to give users access to other groups by being invited to one main group, and this would also allow us to give a group of users different permissions inside other groups based on their membership of that main group.
We currently do this on G Suite to give all members of the organization access to the support email and give other special groups admin privileges in other groups of the organization.
This also makes things simple for us if we choose to move users to different teams, as we only need to edit their membership of one or couple main groups as it automatically edits their permissions across the entire organization for those smaller groups.