Just a idea how I see the grouping, the main downside is that it will only work on the 2D viewport, like the gizmo box.

1) Select a couple of objects




2) Hit the group key, a little request box appear with a default name.


3) The little blue sphere allow to quicky choose a color


4) Done.


Of course, there are a lot of questions allready, like what appends if I hit the group key when I'm in a full 3D view ... well ... I don't know :)
Just like the idea to manage groups visually in the viewport.