Scenario:
I get a mail from Foo Bar about a problem. I add the issue to Bugzilla and would like Foo Bar to be the reporter of the issue so it will be possible to do searches on issues reported by this individual etc.
I understand that I most likley will have to create dummy users for every reporting person since Bugzilla only works with the users in it's system. But if I could live with that, would it be possible to accomplish this?
The only way to do it would be to actually log in as the dummy user when reporting the bug. (Or if you have permission, use the impersonation feature.)
To make the reporter field editable on the bug submission form, you'd have to edit the source code.
The impersonation feature is documented here. Quoting briefly:
You may start a session by going to the Edit Users page, Searching for a user and clicking on their login. You should see a link below their login name titled "Impersonate this user". Click on the link. This will take you to a page where you will see a description of the feature and instructions for using it. After reading the text, simply enter the login of the user you would like to impersonate, provide a short message explaining why you are doing this, and press the button.