I made a new topic for this year: GSoC 2020: Outliner Discussion and Suggestions. Make sure to read the first post and see what kind of feedback I’m looking for this summer.
@RobWu @eobet take a look at 2.83 and 2.90, some of the context menu operators are fixed. 2.90 has fixes for deleting as well. Some of your other suggestions were a bit old and have been fixed as well.
Also, @eobet, with a small developer to user ratio it is very hard to record and implement all feedback, but I tried really hard last summer: https://wiki.blender.org/wiki/User:Zachman/GSoC2019/OutlinerIdeas
@jesterKing or @dfelinto I think it might be good to close this topic now, could that be done?