I still think it'd be cool someday for Trek to explore the origin story of the Borg. I picture them starting out as some advanced, but relatively normal humanoid society, with a small group of scientists experimenting with cybernetic enhancements. These scientists group about a dozen or so of themselves into a hive mind as an experiment, and after awhile grow to like the sensation. Eventually they start to hunger for new voices to add to their collective, and start recruiting people to join them either via coercion, deception or force. Then, before the rest of their society becomes fully aware of the danger they pose, they start rampaging across their planet, and eventually start branching out towards other worlds.

The tricky part would be keeping such an origin story distinct from stories like the origin of the Daleks, or the Cybermen story in the 2nd season of new Doctor Who, as just typing that out I could already see some parallels. But Trek has already someone started putting some of the building blocks for such an idea into place with the Voyager episode "Unity," where a group of former Borg end up coercing Chakotay to help them by connecting him to a small hive mind of theirs, and imposing their will on him.