First on the shipping side, I say it's completely alright to keep Sakura's part 1 self exactly as she is. Part of her character development would have been getting over Sasuke and realizing that she is idolizing a man she does not even know. Kinda expected her development after Sai's "I know your smile is false".
As for rewriting things the way they have been, give Sakura more moments then just Sasori and actually explain everything Kishi never answered, like why was Sai following Sasuke when Hashirama gave him a power he never ended up using, why was Tenten given a scroll and mask she never used, what the flap happened with Yamato, and don't destroy Karin's or Sasuke's character in chapter 627 (Sasuke forgave Danzo and Karin forgave Sasuke - none of that).
Have Kakashi and Hinata die against Pain. The village is not revived. Have White Fang be one of the zombies. Have Juugo meet up with Zombie Kimmimaru (honestly I thought it was stupid that he could sense Madara and never bothered seeking out Kimmimaru to have one last talk).
Also, I'd love to help and be a co-writer/assistant. Please text me. I have so many ideas I want to share to make the ending a "good" ending but not "candy fairy tale happy" ending while showing how rich the characters actually are.
I agree with everything except Kakashi dying. Only Hinata should die.