Just an update on your requests:
Amazon Drive is already supported but it is not included as part of the free connectors. You require a Personal Cloud or Business Cloud Account to get access to it.
I'm not sure about Amazon Music or how you would get access to it. I believe the music within this is protected by DRM and only available via the Amazon Music App.
Re Google Photos, there is no official Google API, it seems to be using the old Picasa Web Albums Data API and that is starting to have functionality deprecated.
WD MyCloud NAS supports FTP (http://support.wdc.com/knowledgebase/answer.aspx?ID=2680) which SME already supports but you will need a personal or business cloud account to use it as it is not available for the free account.