Delegate Group Admin permissions to manage membership and group home page

We have a large B2B community where we need to be able to delegate ongoing management/ administration of Groups to people other than full platform admins.  

Specifically, we need to be able to designate a superuser or other employee (or perhaps a custom role?) to administer aspects of the group experience.  Not necessarily initial creation of the group, but after that we need to delegate these activities to a Group owner or set of owners:

• review membership applications / roster updates
• update home page curated content widget and sticky topics
• (Ideally) create articles within the group