In reply to:

The problem is that I (as I assume all of us do) have an mind's-eye view of the characters, and Jackson's ain't the same as mine.

I saw an interview with your bearded compatriot(?) in which, once I could understand his accent, he mentioned that very point. He said that since everyone would have their own mental image of the story, it would be the kiss of death for him to attempt to form some sort of amalgam of various views. He felt that the best thing, in fact he said the only thing, he could do was produce a trilogy of films consistent with his own internal vision, and hope that at least some others liked it. I think that it's not a bad philosophy for tackling such a task.