An access control system can be as inobtrusive to sketchup workflow as the advanced scene settings. The can reside on a details pannwl in outliner. The outliner filter can be revamped to have the system. And noone would notice it there.
However, unlike the current save as and reload features for external components, it should work flawlessly, whatever the collaborative environment, one has to insert himself into.
Only people who know it would use it and, if you’d want, you’d simply allow everone full access and you would have your system.
The problems arise when you don’t want everyone to have full access. That’s where the component/folder annalogy is valid.
The thing is that as architwcts we want to grant access to upper hierarchy components and lower level components, to different people at same time, and right now, this isbpretty much unmanageable.
If it would be all in the same model… It would be even worse.