“The crew saving JFK sounds silly, but would have been interesting to see. Let me guess, they’re going to say that in the real timeline Kennedy always survived?”
I got it a bit wrong – apparently, the idea was that the Klingons changed history via the Guardian of Forever, seemingly so that the human race doesn’t exist (not explained in the articles, but I’m guessing – from both context and because it’s Roddenberry – that this involves them interfering with the Cold War rather than the simpler thing to go back and interfere with evolution). The Enterprise (not sure why it hasn’t changed) goes back in time to stop this, but accidentally crashes in November 1963. A UFO crashing is big news, and so JFK cancels his trip to Dallas. It sounds like Gene was planning on going with “Tomorrow is Yesterday” time travel logic, and that when Kirk fixed whatever the Klingons did, the rest of it would just kind of fix itself. When they get back to the present, everything is fixed except McCoy is married now. But then there was a subsequent rewrite where they leaned more heavily on being a “City on the Edge of Forever” knock-off and felt that the crew needed to kill JFK to fix history. There seem to be quite a few people making the claim that there was an actual draft where Spock was the gunman on the grassy knoll.
To be honest, I would kind of love it if this movie existed, but I don’t think we would’ve gotten any more if they ever made this one.