I think you have a good argument there - money talks, as they say... you would think they would do everything they could to please their solid fan base i.e. stick with the story and don't decide you knew better than Lewis how it was 'supposed' to go.
Exactly. Some changes, ie a characters hair color are irrelevant. As I've said before, look at Georgie Henley. While she isn't "Golden haired" as Lucy is supose to be , personality wise and performance wise, she is our little Lucy. ( for that matter does her hair color really tells us anything about Lucy as a character besides how well she can sun burn? On top of that Pauline Bayens kind of drew her with brownish hair too.) I think for all us fans she always will be that to us. Thats why after sh's doen with Narnia, I may not go see very many movies with her in it as I dont' want to wreck Lucy for myself as she is my favorite charcter in Narnia.
Or say the Air Raid on London at the begining of LWW, it was perfect as it helped set the stage for the story ( and refuted the idea that it had to be set in the present day to work). Or the Battle of Beruna. We hear it mentioednd in the book, now we see it.
Or take something really minor. Putting Peter and Edmund in armor for the battle of Beruna. Even when I was a kid I always thought it was dumb in picture books and even the BBC films that neither of them wore armor into battle.
On the converse you have say the Night Raid, which while I enjoyed it, at the same time I felt I was watching the Battle of Helm's Deep in LOTR. And in the case of Helm's Deep that was actually in the book. I felt like they were just trying to the crowd aon the message boards aintitcool.com, ( who savagely tore apart not only Narnia, but LOTR, HP, Twlight, Star Wars, Star TRek, The Dark Knight.. lets face it, they like to hate everything.)
Ironically, when Adamson went to Peter Jackson for advice before starting the Narnia films, Jackson told him to respect the fans. ( Granted Jackson had the much more complicated narartive to try to adapt with a number of charatcers, like Tom Bombadil, who'd only hamper the flow. Plus, judging by the number of changes Tolkien made to his own material, I doubt he'd object.)