Idea: We need to Expand /admincp/user.php
 

/admincp/user.php?do=find

To be more direct the search results of users needs inline edit select boxes and a dropdown at the end of the page results to mass move, to new usergropup, delete, ban.

EX:
AdminCP => Users => Search for Users
- Email: yahoo.com
[Find]

Now this will show all users with "*.yahoo.com" e-mails.
:up:

- Need inline select boxes and dropdown.

AND/OR

Take "Prune / Move Users" (user.php?do=prune) and expand what it can search for as detailed as Search for Users (user.php?do=find).