This would be extremely useful and compliments the Category Moderator functionality nicely. In our use case, we have two groups per Category: Moderators, Members. In an ideal world the Moderators are also the owners of Members. This means that when an admin adds someone to the Moderators Group, they are added to the Members Group as Owners.
I’m not sure if this is the thread you meant @sam? It was the only one I could find with reasonable value towards this Topic.