To me, witches in storybooks look like the way ordinary women would have looked when the torturers had finished with them - pallid skin, twisted hands, black eyes, scraggy hair and so on. I've never seen Jewish women in them at all, but I wasn't looking, and neither would children be. Adults would have to put those ideas into their heads, and a child with parents who would do that is probably doomed anyway.
I heard that the witches would stay as is, with an added couple of lines saying that many people wear wigs for all sorts of reasons, and there is nothing wrong with that. It sounds a bit po-faced, but in the unlikely event that it occurs to a child that Dahl's witches are supposed to represent Jewish women the rider would cover it.
I think Miss Trenchbull is supposed to be scary, and she's so OTT that children aren't likely to believe she's real. Mine enjoyed that sort of scariness.
Fat/enormous - I don't know. I'm another who can't see the advantage of one over the other. It seems a bit hypocritical to me anyway - there is so much fat-shaming by politicians, the media and adults in general that it's no wonder children latch onto fat as a reason to bully one another.
I don't understand why Oompa Loompa have to be gender-neutral. Apart from not believing in 'gender', it doesn't seem very inclusive to single out children who claim to be 'non-binary' as a separate species. That one is lost on me, really.
I'd need to see more detail, really. I do know, however, that I wouldn't have read my children the books I grew up with if they hadn't been altered, and even my generation read bowdlerised versions of Grimm's Fairy Tales. It's just progress, really. From what I've seen (which is just a few newspaper summaries) the changes won't alter the stories or the magic.