I dunno, having Yar's baby momma show up and drop off a kid would have been a challenge to write in the late 80s / early 90s.
VindictiveJudge
Something I would have liked to have seen is Vidiians being assimilated by choice on the basis that being part of the Collective had to be better than suffering from the Phage. Instead of them just being enemies, they should have really leaned into how horrible it would be to live with that plague hanging over their heads. It's also implied in an episode or two that there are uninfected populations somewhere, probably under quarantine, which would have been interesting to explore.
There are actually differences in the Prime and Kelvin timelines that happened before Nero's incursion. For instance, Kirk's date of birth is off by several months. They tried to justify that afterwards by saying something about the event sending shockwaves through time to change things before it even happened or something like that. The real reason probably lies in that interview where JJ Abrams admitted he never liked Star Trek, but you could argue that the removal of various down-stream time travel events, like the events of "The City on the Edge of Forever" likely not happening in the modified timeline, could actually cause retroactive changes to the timeline.
But anyway, the Kelvin timeline already diverges before the Kelvin-Narada thing, because reasons.
I was thinking maybe a seahorse kind of thing.