Well, if Carol Marcus ends up with anyone other than Kirk, that is something. Ditto Uhura staying with Spock. The destruction of Vulcan is BIG. Or it could be. Should be. One can imagine something impressive happening if the Doomsday Machine is discovered sooner. Who knows what civilization might have been destroyed before it ran into the Constellation? Maybe somebody who'd make a major impact on the timeline? Gary Mitchell. He's presumably still alive out there somewhere. But without godlike powers that warp his personality.