But first, let's acknowledge that Spock's job might initially seem rather difficult. After all, unlike Picard in First Contact, Spock has arrived not minutes after the timeline change, but decades. And, whereas the Borg were in a tactically inferior position on arrival, Spock's position is worse still . . . the powerfully-armed mining ship is in position and ready for battle, compared to Spock who literally just pulled his ship out of a frickin' black hole. Even if Spock's surrender seems "all too easy", we do have to grant that his situation was at least very close to "screwed".
So yes, we can grant that the writers could've had a good way of avoiding the existence of an easy timeline repair option had they kept slamming Spock with bad luck . . . after all, if Picard and the Enterprise-E had rammed into an asteroid or something upon exiting the Borg time vortex thingy, there would've been no one left to de-Borgify the timeline.
However, any such notions are quickly dashed by the simple fact that Nero lets Spock go. And he doesn't even let Spock go on some remote unknown planet where he'll die a painful death. No, he sets him down on a planet within sight of Vulcan and at a location within walking distance to a Starfleet outpost. And then he leaves.
Nero thus appears to be completely ignorant of Trek time travel in the original Trek universe. Because frankly, if I were a maniacal badguy from the future bent on destroying the Federation, I'd be damned sure that any other future-people opposing me were very very dead. After all, future-people have already demonstrated a grasp of time travel, so there's little sense in waiting until they remember it again.
And if Trek 2009 had shown our Spock, then our Spock wouldn't have been so distraught over losing Vulcan, because the next step would be to fix it. Did Picard see a Borgified Earth and go "aww shucks"? No. He immediately planned and promptly executed some Borg ass-kicking, quantum torpedo style.
But I digress. Spock is left on a planet with kinda-sorta spaceflight capability (in the form of a busted-ass shuttle), communications capability, and so on. Even if we ignore how Kirk drops in on him, we can still presume that he has the capacity to leave the planet within a reasonable timeframe. It is further possible, if not likely, that he would gain access to a proper ship, whether by sharing intel with whatever remains of Starfleet or by other means (e.g. mind-melding with living Vulcans so you have a very logical, very efficient, and very discretely very pissed-off group of people on your side). Even a one-man ship of decent range would suffice (provided it didn't look like a frakking jellyfish).
And with that, he has the timeline in his hands.
And so here are Spock's time travel options that he ought to know about (usually due to direct involvement), listed roughly from best to worst:
- 1. Check and see if anybody's found the Guardian of Forever yet. If not, then you have a time portal all your own.
- 2. Spock may still recall the formula for the slingshot maneuver a la The Voyage Home. Even a Klingon Bird of Prey can do it, and they suck.
- 3. Spock may recall the engine implosion formula as employed on the Enterprise whilst in orbit of Psi 2000 ("The Naked Time"[TOS1]). This one's a little worse off since the tech is so different, but it might still be plausible.
- 4. Spock may be able to calculate the 2258 position of the "black star" near Starbase 9 as referenced in "Tomorrow is Yesterday"[TOS1], and use it in a similar manner as what occurred once before by accident.
- 5. Spock knows the fate of Sarpeidon, a planet whose sun went nova in 2269. Someone there created the Atavachron, which sent an entire planet's population back in time. Surely it could be modified to send one guy back to a specific point when a ship could be available for him. But it seems this option would be awfully tricky, not to mention tough for Spock.
- 6. Though he's missed the Nexus energy ribbon by just four years, Spock would likely be aware of the thing that 'killed' Kirk aboard the Enterprise-B, and would likely have learned of Kirk's brief reappearance. It seems likely he would be able to lay in wait for the Nexus when it returned in 2293, or at least pass on the information to Vulcan's survivors.
Okay, so once we can get Spock to the past, what does he do?
The best possible outcome is that he somehow prevents the formation of or somehow 'collapses' the singularity from which Nero emerges in 2233 before the Kelvin ever notices it. Presto-change-o, the future is altered and with it the past. (After all, they do a lot of time travel in Trek.)
Thus the timeline of the entire film is excised, and we again have TOS. So even if there was a Captain Robau of the USS Kelvin with a Mr. Kirk on his bridge, it would all be TOS-ified and not a lick of it would look anything like what we saw in the movie.
Methods of accomplishing this goal could vary, and many would venture toward technobabble. The easiest and most cartoon-friendly solution (thus matching the Abrams film) would be to be able to acquire more red matter via some adventure (no doubt battling Romulans and Klingons along the way) and drop it on the right spot so it spits Nero back out in the future before he even appears in the past, preferably at the Arkham Asylum star system or something.
Other techniques could be more complex or too damaging. For instance, causing a supernova of the star near which the Narada appears would save Vulcan, and depending on the timing the Kelvin could escape, but such a move would be likely to have other repercussions on the timeline. But I mention that example in order to point out the fact that our Spock ought to be thinking of whatever was effective, and can't be afraid to think big.
For instance, merely destroying the Narada upon its exit from the singularity is unlikely to fix the timeline, because the Kelvin was already there. However, if you can somehow manage to guide the Kelvin away from the event and then destroy the Narada and send its parts falling into the nearby sun, then you're just about golden.
After all, in TNG era Trek it is made pretty clear that the timeline is not quite the fragile thing we might expect. One might think the slightest alteration to the timeline would have ramifications not unlike some sort of chaos theory exercise. Merely appearing in the past and standing in a city ought to immediately wreck the future, just from adjusting the courses of the city-dwellers . . . this lady advances a second along the same path, this guy loses a second along his path, this other person turns left entirely. The result is that the first two people, the parents of, say, Colonel Green, never met. And Zephram Cochrane's father was a friend of the guy who turned left but the guy who turned left twisted his ankle two blocks later, missing his interview and with it the job, never meeting Cochrane's father and never introducing him to Zephram's mother, thus Zephram Cochrane did not exist either.
But with DS9, certainly it is explicit that for those who travel into the past, their present (our future) can be the same despite all sorts of minor changes. The same is even true, though, of First Contact.
Thus, what we might call Temporal Inertia is on Spock's side. Keep the change from the original small and it will fall into place.