Thanks)
So, when I am talking about scene complexity it is not about my scenes and my setups, I am talking as a project manager that works with setups made by other artists.
From my experience, artists are pretty much bad at creating clean scene hierarchical structures, so their setups almost always falling into mess.
Thats why I putting lots of efforts to make hierarchical systems clear but flexible in order to survive complex projects.
Collection engine is too much overloaded already, so I can’t say that putting grouping ability to the static context - to collections - is a good idea.
The ability to turn non-cumulative collections to groups and work with them as with groups is nice to have, but, for example, the process of creating collections by grouping whatever random selected objects will bring the need to separate regular collections from created as groups, otherwise we are mixing static and dynamic context separations in the outliner.
Thats why all other software that provide common grouping handles groups separately, keeping outliner clean.
From the one side, separate groups engine is industry standard, that will possibly bring some formats compatibility, from the other side, collections are needed to be handled as groups, and separate groups will not have rtos (otherwise rtos management will be split to impossible to properly controled mess)
So, in overall, there are too much things to design, to anticipate and to think about.