One work around that I've thought about but have not tried would be to use SubmitToSharePointList after running the SaveToSharePoint command to update the metadata of the item. Unfortunately, since the mapping tool for that command doesn't currently surface libraries, it involves hand editing the mapping, and it will also involve figuring out a way to query to get back the list item ID for the attachment you just saved to SharePoint (I'm thinking that could be done w/ an owssvr.dll data connection and the link for the item).