YARN
Fleet Captain
Here's some food for thought:
1. Possible timeline #1: Cochrane makes his warp flight by himself, with no help from any future time travelers or problems with Borg incursions. He catches the interest of the Vulcans, and ultimately leads up to TOS. This theory makes the most sense when we view "Metamorphosis," as Cochrane truly seems not to know who Kirk and Spock are or where they came from, implying he had no past contact with Starfleeters from the 24th century.
I think we should eliminate this as a timeline as this is merely a subset of what you call possible timeline #3.
2. Possible timeline #2: Cochrane makes his warp flight with the help of future time travelers from Starfleet after the Borg damage his ship before launch. It is still a successful flight, he still meets the Vulcans, and it still leads up to TOS, so when Picard and company return to their own time, it's still the same timeline because they were always meant to travel back in time to help Cochrane. Unfortunately that doesn't explain Cochrane's reaction to meeting Kirk and Spock in "Metamorphosis." He should already be aware that people like them exist, because they came back through time to help him. Unless he's being deliberately coy. This theory would invalidate theory #1.
Right. Self-completing causal loops don't work in instances of
"proliferating universes".
As for the episode "metamorphosis" we simply cut them a break and give them some wiggle wiggle room with regard to inter-franchise details. For example, no one gets bent out of shape that Cochrane does not look like himself in First Contact (i.e., he is played by a different actor) because we allow for wiggle room on certain details. It is minor nitpick on the level of "James R. Kirk."
3. Possible timeline #3: Cochrane makes his warp flight with the help of future time travelers from Starfleet after the Borg damage his ship before launch. It is still a successful flight, he still meets the Vulcans, but because of Cochrane's knowledge of the future, it becomes a diverging point in time, creating an alternate universe where things turn out a little differently than in TOS. Picard and the Enterprise-E either return to the future of this new timeline (similar to the events of the end of the first "Back to the Future" movie), or they return to their own universe's future, depending on how the laws of time travel work with the chronometric particles the Borg created. But if it's the former, then obviously the events in "Metamorphosis" don't count anymore because it's from the previous TOS timeline which doesn't exist anymore. This is possibly the universe where ENTERPRISE exists, and if the Enterprise-E returned to the future of this new timeline, then "Insurrection" and "Nemesis" also take place in this new universe, which would explain the ENT references in "Nemesis" where there weren't any before. However, what it wouldn't explain is TATV, unless the events that Riker and Troi are recreating were from the original timeline of theory #1 or #2 (which would explain why the ENT characters acted completely different in TATV than in the rest of the series; why no one got promoted in all those years; why Shran was a jewel thief instead of a member of the Imperial Guard; why Trip died in the stupidest way imaginable; etc.): ENT takes place in the timeline of this new universe, while the recreated events of TATV take place in the timeline of the original universe, since TATV took place during the time of "The Pegasus" in the original universe.
As much as I would like to think that theory #3 is the best one (and theory #1 if there hadn't been all this mucking about with time-traveling), the visual evidence seems to mostly support theory #2.
Thoughts?
Theory #3 is not as simple as you seem to think.
You say
1st time around Cochrane does it alone and is (therefore) surprised to see Starfleet in TOS.
2nd time around Starfleet helps Cochrane and (therefore) the events of "Metamorphosis" no longer exist.
But we aren't done yet!
This (2) universe is still SO incredibly similar to the (1) original "first time universe" that Picard and friends return (in Enterprise #1) to a future where a Borg sphere went back in time from a Borg cube and (more importantly) that Enterprise (#2) followed back in time.
Therefore we have a....
3rd time around where Enterprise (#2) goes back in time following Borg Sphere (#2). This fractures the timeline again. Remember, it was a slightly different Enterprise crew (#1 Enterprise) with a slightly different history that helped out Cochrane in round 2. This time, it is the turn of Enterprise crew #2 to help out.
and this leads to.....
N-times around where N equals infinity. We have created an infinite number of universes, with an infinite amount of matter and energy between them, all by simply going into the past.
Are you sure you like #3 better than #2?