Search for tickets updated by a specific non-privileged user

Hi,
We have interns who rotate through our department, and while they are here they are given privileges in RT. Once they leave our department, they are no longer privileged, but it is sometimes useful to find all of the tickets which they updated. I know that the Query Builder can easily create a search for all tickets updated by a privileged user and we use that, but we need to find tickets updated by no longer privileged users. We’ve been doing it by editing the query URL in the browser, but that requires careful typing of the user’s name into the coded URL. Has anyone created an Extension which adds a “Select a user” text field to the Query Builder so that non-privileged users can be selected for a “Updated by” query?
If that doesn’t exist, does anyone else think it would be useful?

We’re running RT 4.
Thanks,
Ari