It is recommended that when merging databases that all users' security roles should be set to manager or Administrator. Not a problem if you have five users, but if you have 55 or 105 that's a lot of clicking to do this one at at time.
What I would like is the option to make all users administrator with one click, then to set them back to their original settings with another click.
In fact, is it not time to resedign the Manage Users user interface to be better suited to larger installations.
One big table where you can see and make all the changes would be my choice.