You know, since we've been talking about Endgame, I'm really starting to rethink some things about Janeway's motives.
We learn in Star Trek '09 that Nero & Spock going back in time to the 2230's only created a new timeline going forward; it did not erase the old one.
Now with that info in hand, let's look at Admiral Janeway's actions. Despite a complete lack of concern from both her and the people helping her (Miral Paris, Reg Barclay, Harry Kim and the Klingons), that she will be erasing the current timeline and them along with it, she succeeds in doing so, all for the selfish reasons of keeping Chakotay and Seven alive and together (fuck you, Carey!)
But does she actually erase the timeline? Based on the logic shown in the Abrams films, all she would be doing is creating a new alternate timeline in which Voyager gets back to Earth in 2378 instead of 2394. The actual "prime" timeline where we see the events of 2404 would still exist, which would explain why Miral and everyone else doesn't seem to care that Janeway is doing this. Apparently all Admiral Janeway wants is to create an alternate universe where her own personal wants are fulfilled in some weird bastardization of 'therapy' for her. (I doubt that was the intention of the writers, but there you go.)
So there are three possibilities here:
1. Admiral Janeway went back in time and knowingly erased the 2404 timeline for her own personal selfish reasons.
2. Admiral Janeway went back in time to 2378 in an effort to create a new alternate branching-off timeline where Voyager got home early, Chakotay and Seven don't die and hook up instead, and Tuvok doesn't go crazy.
3. Admiral Janeway went back in time but wasn't aware if her actions would erase the timeline or create a new alternate one.
Here's the problem with option 1: Why on Earth would people like Miral, Barclay, Kim etc. be helping Janeway with her selfish scheme knowing that their entire existence along with their entire universe will be erased? And why would the supposed Temporal 'cops' from the 29th century allow this to happen, or let her bring future technology into the past?
Here's the problem with options 2 & 3: Knowing that Admiral Janeway would probably have to sacrifice herself by sabotaging the Borg with her pathogen, why would she even bother creating this alternate universe when she won't even be alive to see the fruits of her labor? (Especially since her changing the timeline resulted in not only Chakotay and Seven NOT hooking up or having anything to do with each other, but Seven becoming some silly vigilante and having a relationship with Raffi instead! As Jerry Seinfeld would say, not that there's anything wrong with that, but that was obviously not Admiral Janeway's intention for doing what she did.) What if Admiral Janeway's actions still ended up causing Chakotay and Seven to die, just in a different way? The former could easily have been killed when the Protostar was lost, and the latter could have been killed while working for the Fenris Rangers.
Clearly, Admiral Janeway's actions are not remotely logical, nor are the actions of the people helping her. Whether she set out to erase her timeline or create an alternate one, her motives simply don't stand up under close scrutiny.