This is making me miss not having new Fringe tonight :( Although, they are presenting an interesting question with this plot line. How do you make everyone remember you if you never existed? Although, I'm not looking forward to lots of Peter yelling at people about why they don't remember him. Feels like the "we have to go baaacckk" era of Lost.
I think the whole Peter remembering EVERYTHING and them not remembering him, or only remembering him as some kind of dream, is genius. That suddenly makes Peter god-like, at least with respect to timelines. But what if you are a mortal god and no one trusts you? It is a daring place to take the story, provided they don't get caught up in melodrama.
And now the season can finally begin. This is how it should have kicked off.
You did kind of need the setup for this. But yeah, it could have been done in one episode. Maybe two.