I doubt the workflow could be any more complex than what you have seen. In many ways, it should be less so. There are some nuances, however. Partly the problem is the extreme egos involved in many business negotiations. Every communication sent has to help the sender to look good. There has to be a bias against publicizing changes before the author is done. There also has to be flexibility to override approvals. A lot of big deals would never close if someone had to take personal responsibility for waiving closing conditions that aren't satisfied at closing.

Regarding hiding changes until they're done, that shouldn't be in feasible except that you (or your counterpart) may not want to use a system owned by the other, because you lose that guarantee. A third party hosting it could offer that (naturally), but takes on extra liabilities with securing the documents in progress.