Zigūr, like
Kuruharan, I was interested in what you said here:
While Tauriel is a deliberate inclusion, I can't help but wonder if a lot of the "changes" exist simply because they couldn't be bothered to read the book closely and see the details that were already there, perhaps because they assumed that, as ostensibly a children's novel, there couldn't be any detail (when in fact there was plenty, but they had simply forgotten that it existed or never noticed in the first place).
My opinion is that many of the 'changes' were perhaps due to decisions on how to fill the gap resulting from the decision to have a third film...