Hi Martin,
I'm looking at the same challenge. The ES bundle for managing external warehouse is all very IM based wth deliveries and good movments. I'm also looking at a ES repalcement for the external warehouse management scenario based on using the warehouse transfer orders send from SAP to external WMS and updates send back form wms system to confim, or cancel or update.
this scenario is normally based on the idocs wmtord,wmtoco and wmcato but in the scenarios it refers continously to is the good movement ES
any suggestions or are you still waiting for answers ?