It would be really useful if the administrator could perform the following updates/changes on a global basis by selecting a group, by filtering and check/uncheck list:
1) Email users
2) Move users to different group
3) Change users level
4) Select admin skin
5) Delete users
6) Generally normalise the various profile settings
On Groups it would be good to be able to select which User Profile settings a user can change, especially when dealing with a large number of users and you want to ensure that everyone is using the same admin skin (etc).
The administrator/s should be able to navigate into users media folders (I know I can do this through ftp but would be so handier if accessible through the admin console).
...I'll shut up now... :D