In all seriousness, though, I wanted this so badly that I started (and failed) a startup with 12 employees nine years ago to build it. It was conceived for use in working with "big data" but the system essentially provided Etherpad-like scrubbable versioning of all common office document formats as a side-effect. All of it was structured in an environment more similar to the social aspects of Github than Dropbox, but you could sync up to your filesystem via a FUSE wrapper. That is, people could easily follow or fork your work in progress. If we'd continued, you'd have been able to accept the equivalent of PRs on your Word docs.
It was so awesome that we couldn't find anyone to pay for it, sadly. Armchair quarterbacks would fairly accuse us of failing to do proper customer development.
I can't speak to the technical limitations of Dropbox's versioning implementation, but given that they already have both viewing AND versioning running for a decade, I honestly can't believe it would take more than a few months for a small team to implement Etherpad-like editing functionality for the office suite document formats.