I’m totally cool with the idea of Writer X coming on to a book and deciding that she/he wants to change the characterization of a character. I mean, if I think the change is a poor one it’ll irritate me, but at least it’ll be a case where I get it – the writer has to have the freedom to change things up, whether I like their decision is a whole other story.
Now here’s my issue, though – I think that if you DO do that, you should at least “have” to explain the change, and here’s why…
The main argument in favor of allowing characterization changes, and it is an argument I’m basically in favor of, is that you have to give writers the freedom to write the story they want to, and they can’t be expected to be beholden to continuity.
However, when you take an established character and make a major change to said character, what you’re doing IS intentionally EVOKING continuity. You are using Character X because you WANT the continuity behind that character. You could just create a new character for the story, but you WANT to use an established character instead because of that very same continuity.
So when you opt to USE the continuity of the character, THEN I think you should be expected to at least address the changes you’re making with the characterization of the character.