This version of NIM with the Google Apps driver seems to be perfect for a project I have in mind.
There is an unofficial application, GAM, that has the capability to perform this, albeit from the command line (not so scary to old school sysadmins like me)...
Google Apps Domain - acme.com
Google Apps Secondary domain new.acme.com
Google Apps Secondary domain old.acme.com
Can a user, firstname.lastname@example.org be renamed/moved by NIM to email@example.com ?