With all so respect, my intentions have nothing to do with collecting data. With that being said, you raise a good point, and thus I would also be interested in a way to wipe the iPhone backup off the RPi after the target iPhone has been restored. That way there is no personal information being stored after the transfer.
As for "Personal Device" that is an assumption, based on no facts. It will be left at the store, locked up, where our store computers are. It will never keep personal information, nor will it ever leave the store once in operation.
Apples tools are not shitty in my opinion, its our stores computers using apples tools (iTunes restore/backup) which are shitty since they wipe each day, and have to re-install all the iOS firmware. In addition to having 80GB hard drives which don't often have enough memory available to complete the backup and keep a store copy of all iOS firmwares.
Off to go learn about the WCGW, thanks for the share.