My biggest issue with grouping objects, and I imagine many other have this gripe as well, is that you can’t see the outlines around an object that’s in front of something already in a group, so if you want to move something like a room then it becomes very difficult to know what in that room is going to move with it.
My idea is that instead of just an outline, objects are also highlighted, so if you select a group then everything in it will turn pink.