From what we can gather the Nerevarine went to Akavir. What if he/she learned how to become a dragon from Tosh Raka either by forcing him to teach him/her or just sitting down and learning? Then the events of the Red Year, Argonian and Nordic/Orcich invasions, Umbriel and even Skyrim's Civil War begin to happen. What if the Nerevarine as a Dragon then flew back to Tamriel to check in on things? That way we could evade the what race he/she was kind of thing and we have the Nerevarine in Skyrim and it is Lore friendly.

Anyone think that would be great or a colossal waste of time on my part typing it out and your time reading it?

In this case, to become a dragon means to become a divine. If simply teaching people this was so simple, Auriel would have done so for the Altmer a long time ago. And Tosh Raka would have taught the Ka Po' Tun on how to become gods, too. But you need to kill all the snakes and men first.