BulkEdit can force the display names to be "first last" or "last, first" if that works for you - this can be applied to any subscriber types, including AMIS users - if your display name needs are more custom than that, then this wont do what you need.
The Unity Bulk Import tool can update standing users and one of the fields it can update is the display name - I _believe_ this can work with AMIS subscriber types but don't have a system to verify that on. If you open the Bulk Import Tool (found in the tools depot on your desktop) and reference the help, it'll show you how to construct the CSV file to use for this purpose.