The backup is a ZIP file so it can be opened with any ZIP file utility or with File Explorer if you change the filename to .ZIP.
You can accomplish what you want manually. Open the backup, drag the .RMGC file to your desktop. Rename the backup. Drag the database file to where you want it stored. Simple enough to do.
The goal is an automated restore rather than a manual process, with the restore going to the same folder as the original RMGC file and with the restore not destroying the RMGC file that's already there. If the RMGB file is a real ZIP file in disguise, it should be possible for RM to rename the file that's embedded within the RMGB/ZIP file before the restore.
I didn't know that an RMGB file was a real ZIP file in disguise. That's good information. I'm familiar with the concept because KML and KMZ files work the same way. A KMZ file is a compressed KML file. If you rename a KMZ extension to a ZIP extension, you can see and manipulate the embedded KML file with any ZIP utility including Windows File Explorer itself. In the other direction, if you have a KML file and need a KMZ file and don't have a KML to KMZ converter, you can zip the KML file and then rename the resultant ZIP file to a KMZ extension.