Hmm, I'm not that impressed with RS's file handling so I tend to do anything of that ilk outside it.
It might be worth investigating some of the general batch renaming tools that are out there for the renaming part. You could then use the 1-2-3 flagging in RS to group RAWs, move the flagged files into a new directory and run the renaming tool on the contents of the new directory.
Clunky I know but it might be an option.