I'm not sure how this would work in practice. GSW is last mile only, so a seller dispatching through GSW doesn't really make sense. Would be open to hearing a use case for your hypothesis though.
Amazon will be launching FBA pretty soon too which will allow sellers to let Amazon fulfil their orders. I'm sure you guys are all over this.
Until there is clarity about the Amazon deal, assume it doesn't exist.
GSW Price at posting:
43.0¢ Sentiment: Sell Disclosure: Not Held