When cleaning up a user database, it can be quite time consuming to edit the default role and company of users. the interface only allows you to edit one user at a time and you have to consistently scroll to your previous location on the user list once you make an edit.
other items I think might be helpful for admins with large user lists: The ability to filter users by project names or other meta data like role, permission settings, etc. Just something to make managing the user list a bit easier.
Also the BIM360 API doesn't allow for the reimport and change of much of the users' data.