I just don't agree with any of that. I don't think Disney cares about Carrie Fisher or Mark Hamill's feelings or the fans or the legacy of Star Wars. I just don't think they do. Look at Marvel. It's a money-making machine, but it's a machine. The movies get made no matter what happens behind the scenes, and they hit their release date no matter what happens. If someone steps out of line, they're removed. It doesn't matter if it's directors, actors, producers. They're about selling toys and selling tickets.
The treatment for Episode IX was written in 2014, and the movie has had a director since 2015. The guy who wrote the treatment for VIII wrote the treatment for IX. I'm guessing there were entire story beats written around Leia that flow from 8 to 9. I'm sure Trevorrow has had a vision for the movie the last two years. He pitched it, and Disney's army of suits took his ideas and ran them through the Disney Machine(tm) and it's all been rubber stamped and moved forward.
If Leia was only supposed to have a minor part, I can see them adjusting. But make full-scale changes to the script? Alter the production schedule at all? I don't think the suits at Disney would allow that. Star Wars, like Marvel, is a machine. They could release Squirrel Girl and Jar-Jar's Crazy Adventure and it'd make a billion dollars, and they know it. For every offended person that didn't want to see CGI Leia back in her gold bikini, they'd have ten more people salivating over it.
Ironically, I'd think differently if it was still under George Lucas. I think he genuinely cares, whether or not he has talent. But Disney doesn't.