After thinking about it for a few days, I find myself more OK with the "love" resolution. Mostly because I realise my wish for a more (faux-)scientific explanation was never going to come true, partly because Fringe has always been about the relationships. I still dislike this season's pacing and I still feel the time we devoted to Amber Olivia was extremely disproportionate (we've spent more time on her than we have on Faux, who is an actual person who had an actual purpose in the actual plot of Fringe, coming into contact and having a relationship with Peter, messing up things for Olivia, having Peter's son etc etc). But still.
I'm also over Olivia's decision to replace her memories with Blue Olivia's. I still have a problem, not because she's a woman or because she's doing it for love, more because I can't see anyone so willingly erasing all their memories for any reason, with only mild hesitation assuaged by an anvillicious serial killer, but whatever.
Now my problem is the practicality of it all. Myself and others have said that it's problematic to have characters living in a world that doesn't correspond with their memories at all. If, like Olivia suspects, all her Amber memories are lost, there will not be a way to reconcile her "old" memories with this "new" world.
Peter now has the same perspective as the Observers have (who can see and participate in all possible timelines), and we the audience are being invited (through the human characters) to adopt this omniscient perspective as well.
I disagree with this; Peter has no idea what has happened in the Amber universe. He didn't live it, he can't look back on it like September can. If he did know somehow, then he would be able to help Olivia navigate through her existence in the Amber universe even with just her Blue memories, he'd be able to go "honey you're thinking of the Blue Universe, here in the Amber it happened like this", for instance. But he can't. And Walter may be regaining his Blue emotions if not his memories, but he won't be much help either.
Broyles, Astrid, Lincoln and Nina, on the other hand, don't remember the Blue timeline at all. So how will they interact with Olivia? What will she tell Broyles, "sorry boss but I'm a totally different person now, and I remember a totally different you, lol"? Including totally different cases in her FBI career? At least when Peter did it this season he had an excuse; he was new, heh. Olivia is not new to this universe, not physically, but she will be brand new once she gets her new (but in reality "old") memories. I'm curious to see how this is handled and I think something else will clear things up.
I also have to say I feel bad about losing the Olivia of this season, frankly. We stayed with Amber for 15 episodes, felt bad for her, saw the hole in her heart, and then, instead of something/someone filling that hole, we only got to see her turn on a switch and turn into a different version of herself, the only way she can be happy? That's really sad, in my opinion. Even if she was a Peterless, depressed Olivia that was never supposed to exist. But then I'm the sci-fi fan who always feels bad about people's, like, clones and doppelgangers who have terrible fates. I still remember the Enterprise episode (shut up) about Trip's clone and he only lasted 1 episode. Sigh. RIP Amber Olivia, you will be missed even though you were miserable. Hell, because
you were miserable.