It has been a while but didn't Archer imply the Eugenics happened in the 21st when he was talking about his grandfather?
It was his great-grandfather, but yes, that is more consistent with a mid-2000s time frame than a 1990s one. I've tried to handwave that in my mind by assuming that either he skipped a "great" or a couple of his ancestors had kids very late in life, but this new information does make it easier to reconcile.
I’ve been thinking the best place to split the timeline is between TOS/TAS and everything from TNG after, because that's the simplest break (because of "Farpoint" retconning the WWIII date). But it occurred to me last night that if TNG/DS9/VGR were in a separate timeline from the later shows, it would reconcile the contradictory portrayals of Section 31, as a secret criminal cabal in DS9 and an authorized part of Starfleet in the later shows. So now I’m wondering if I should convert to the longstanding fan notion that the Temporal Cold War in Enterprise altered the timeline from the version seen in the earlier series. Maybe there are three distinct timelines, with most of the same stuff happening but some subtle differences here and there — which would help reconcile the continuity problems between TNG/DS9 and Picard season 3.
Although, as with Spock and I’Chaya in “Yesteryear” or the subtle changes the DS9 crew made to the events of “The Trouble With Tribbles,” (or the Prophets writing Akorem Laan back into Bajoran history), it’s not so much completely separate timelines as functionally the same timeline with certain continuity changes. We can treat the characters as effectively the same people, but with some alterations to their memories and context.
I always resist fans’ desire to use alternate timelines as a rationalization for storytellers’ continuity adjustments. Fictional series tweak their continuities all the time, and it’s only time travel-related when the story says it is. There’s a difference between in-story changes in the events themselves and metatextual changes in the depiction of the events. But now that we have a textual, canonical assertion that time travel has permanently altered the timeline, I have to admit it’s kind of liberating to embrace it as a way to make sense of major inconsistencies that I struggle to reconcile or overlook within a single continuity. I still prefer a Doylist interpretation for a lot of the inconsistencies and weirdnesses (e.g. Discovery's turbolift hammerspace roller coaster), that it’s just an embellishment or error in the dramatization, but I’m contemplating which inconsistencies are major enough to be worth explaining as timeline shifts. Better to be open to using different tools for different tasks than to try to fix every problem with the same tool.
Although I worry that if I embrace it too fully, it would complicate keeping track of things way too much. What about the difference between early TNG, where Data had emotions and the Federation had been at peace for a long time, and later TNG, when Data was emotionless and there’d been a recent Cardassian war? It’s probably best to use the time-travel fix judiciously, if at all. Maybe using it for the Section 31 thing is overkill.
It would be fascinating to see a one off story set in that alternate universe where Kirk's Enterprise had an Andorian first officer. I wonder what other alterations would spin off of Spock's absence.
You'll be pleased to know that exactly that story was told by Geoff Trowbridge in 2008, The Chimes at Midnight from Myriad Universes: Echoes and Refractions. It focuses on how the movie era from TWOK onward unfolded with Thelin instead of Spock, although it doesn't address how the V'Ger crisis was resolved with in Spock's absence.