Star Wars was based around the old cowboy films.
Aside from the awful re-construction, Han's character arc originally has him transfer to Black Hat (A New Hope) to White Hat (Return).
Now, if he didn't shoot first, he goes White, Black, Grey; because he never reaches White again. Therefore his redemption is gone, therefore his character is destroyed.
Same principle for when Vader walks onto the ship at the beginning of 'A New Hope', now that you've seen him as a snotty kid, he's just not as scary. Because Clone Wars leaves him as a Grey Hat.
If he was really going to remake the films, perhaps he should have James Earl Jones alter his voice when the respirator speeds up or many other trivialities that he missed second time around but the breaking the back of the Hero's Journey is like a Doctor breaking the Hippocratic Oath. You just don't do it.
(Ignoring the piles of shit that are midichlorians, 'What, incest makes you stronger in the Force?')