Hi, just a quick thought - in my opinnion world outliner could be greatly improved with simple feautres and shortcuts.
For example: ‘close hierarchy’ and ‘expand’ shortcuts would be my salvation while working on more complicated levels.
As for the feautres, how about coloring items, like layers in photshop? This way I could easily group ‘temporary changes’, meshes I need to redo and so.
Also stuff like: quick lock, filter search by type (or by attributes), visual separation of groups?