Add the option to remove "Preserved Filename" in metadata
Currently under Batch Rename there's an option to "Preserve current filename in XMP metadata" but there's no way to get rid of these preserved filenames after they are no longer useful (or simply because they disclose outdated or confidential information).
One way to do this would be to add a "remove preserved filename" checkbox to the Batch Rename dialog box; that way you could just rename the the files a second time to clear the preserved filename.
Another way to do it would be in the metadata panel; just make the "Preserved Filename" field deletable. You could also add a command to "Remove preserved filenames" to the Metadata panel menu and Tools menu.