I wrote a utilty exactly like that into Kymaera. You can create a GameList, and then click "resource copy".
Kymaera will copy all the roms,snaps,marquees,cabinets,etc.... to a destination folder and preserve the directory structure. I was using it to set up a limited list of games on my new cabinet.
Unfortunately, it's not in the current release, but it'll be in the next.
-PMF