I have a proposal for an future enhancement for WP File Download. Related to GDPR Reasons will for companies in the EU the usage of Cloud solutions like Google Drive, MS OneDrive or Dropbox extremly critical.
So more and more companies works with self hosted Cloud Storage solutions. And the most important one in European Countries was NextCloud, a open Source platform.
Maybe it makes sense to think about a sync solution also for a tool like Nextcloud?