I think Spencer wants to make Peter whole, or at least address some of the issues with the character (such as the constant re-starts where Peter has a good thing going and ends up re-set to loser status). I think he wants to show that OMD/BND affected a lot more things than just Peter's life. I think Mephisto still turns out to be the big bad behind all this, and that Otto's memory loss ties into Mephisto's plans against Peter.