Some shameless self-promotion but here is the result of month-long suffering with Plone 5.0:
The shown integration is not limited to Dropbox. It works out-of-the-box against local filesystems, databases and storages over WebDAV and many more.
Unfortunately Plone 5.0 is not still in a mature enough for running XML-Director 2.0 without pain...that's why
there is no official release of XML-Director so far.
Andreas