Yay! That sounds like it'll be awesome. I can't wait to see Severus take his revenge on Ginny.
As for how Severus decides to get Harry back, there's a lot of things you could do. I like the idea of Snape ending up feeling jealous in spite of himself and accidentally revealing it in front of Harry or Hermione, giving Harry hope. Then maybe Phineas or possibly Hermione could make a suggestion as to how Severus could go about making up for what he did to Harry. Or Hermione could convince Harry to say he won't take Severus back unless Severus courts him and convinces him that he really means it.