It should be noted that even now, about 20 years later, there are still many LOTR fans who are NOT pleased with the changes in the LOTR trilogy. I for one am quite ok. As you said, it's an adaption and things can never be put on screen exactly as it was in the novel. This goes for any adaption.
Yes, I would so love to dedicate 15 minutes of a movie exploring the little details that can be found on the bark of a tree. Tolkien's concepts, as a whole, were genius and inspired, but IMO his prose was WAY too ponderously bloated and over-engineered. I always felt that Jackson did a fantastic job with the property.
Deform the story any more than the Elves being at Helm's Deep at all? Plus, it was pretty badly handled...they aren't even mentioned in the aftermath. It seems less like they were all wiped out and more like they just evaporated from the plot, like if the characters all just went "lets never talk about this part again!". It's possible that Arwen might actually have brought the reforged Andruil with her to Helm's Deep. Form there on she could be easily inserted into the plot of Return of the King, as @Skywalker said, have her take the place of her brothers have in the books. Have her travel with Aragorn to Minas Tirith and have her fight in the Battle of the Pelennor Fields, have the city receive its future queen etc. maybe there could be some drama with him insisting that she stays in the city while he leads the forces of Gondor to the Black Gate. They could have even inserted a little sub-plot with her and Eowyn. I think the moment they made Arwen a warrior, they should have been consistent with that. And as I wrote above, female elf warriors were not unknown according to Tolkien's notes, just unusual and Arwen is the granddaughter of Galadriel and great-granddaughter Luthien, so her taking more of active role would have actually have been a pretty sensible change.
I'm excited. Initially I was not but the production seems to be going in the direction of a compelling story based on parts of the Silmarillion. That creepy Annatar fellow in the trailer was instantly recognizable, I can't tell you why. I'm honestly pumped for this. Give me a solid story, respect the world.
Speaking of changes, Anduril was reforged and carried by Aragorn when they left Rivendell in Fellowship of the Ring.
During the forging of the rings, Sauron was not openly The Bad Guy - he used the guise of Annatar to wheedle his way into the confidence of Celebrimbor. IIRC, Galadriel and Elrond were suspicious of him, but they didn't know why. I don't know if TRoP is planning to make him the openly bad guy or still keep it under wraps.
I would definitely like to know more about Tom than what we've been told. Sadly, I'm not 100% sure even Tolkien knew what he was, outside of "older than the old" and "a particular embodying of pure (real) natural science." Tom is a true enigma and a source of unending fascination for me.
Yes, Annatar WAS in the trailer. And again, there were things in the old movies that were portrayed as creepy when they weren't supposed to. I mean the Elves were kinda creepy in the movies at several points, when really they aren't in the books (I mean what the hell was even going on with Thranduil?). Or the Mouth of Sauron who was just some normal guy in the books but some sort of monster in the movies. There is little concrete description of Annatar except "fair", and the character design is somewhat creepy but also "fair".
I don't know about creepy but definitely otherwordly. Thranduil, in particular, had the most interesting attitude and really emphasized the long lived nature of the Elves, and how it would feel towards the more mortal races of Middle Earth. I loved that alien feel. I didn't find it creepy, so much as he was showing a different side of the Elves.
Well perhaps "otherworldly" is also the better way to describe Annatar in the trailer. What I wanted to express was that I think Annatar in the trailer and the more "otherworldly" depictions of the Elves fit together very nicely. He could very well be just another Elf really when judged by his appearance alone. Though I do think Thranduil was a bit much, he reminded me of nothing as much as of Jareth the Goblin King from Labywrinth ;-)
Somewhat, at least in Desolation of Smaug with Thorin. He was better in "Battle of Five Armies" and his interactions with Gandalf.
Bombadil's power was so overwhelming, yet enigmatic, that he wrote himself into the story and even Tolkien himself couldn't adequately explain him. Every writer knows that these things happen every so often...
This. For ages uncounted, it was said that Tolkien was unadaptable to the big screen. I remember seeing the initial press release and cast list, and laughing my ass off- I literally thought it was going to be the biggest bomb in the history of film. Jackson proved me wrong. So wrong. I don't like all the changes, but by and large, what he did with LOTR worked.