Regarding rebel commanders (and personnel) being changed from film the film, I think that was the only right way to go in terms of story/universe. First, it provides a sense of scale of the rebellion, i.e., they have many bases around the galaxy, and counterbalances the rest of the universe shrinking elements. Second, it provides a sense of how dangerous being a rebel actually is, i.e., even the top commanders might get killed regularly.
I do agree completely. But only one or two would have been enough, and I wouldn’t even have them speak. Just something you could see when watching the film 2000th time in 4K.