I see the option
Helmut Grohne [ Editor ]
You did find the correct solution yourself. To change your email address in all bugs you would send a long mail to firstname.lastname@example.org with lots of submitter lines. Closed bugs get archived and can no longer be modified. In order to modify them you would first unarchive them, then change the submitter and then archive them again (or let the bts do it later). An example mail can be found at http://lists.debian.org/debian-doc/2007/12/msg00027.html. I am not aware of a script for generating such a mail.