Some spoilers may come up, obviously.
OK, so I have a big problem with how the Hobbit films went down. Don't get me wrong, they weren't bad necessarily. But they weren't great either. As films alone, they're cool, but most will be linking them to the trilogy that came before them, LOTR, and next to them they don't compare.
Firstly, I have read the books, but there are so many factors that come into play about the books and movies, that I understand that every film can't be a perfect adaptation to the books, which I will also agree with when I recreate it myself. I will keep certain elements of the books that I like, add a few things I remember, and boom, let's do this.
Ok so primarily, making this into 3 movies, while ambitious, was totally uncool. They added a lot of crap in there that was pointless. I would have liked it if the added content actually did something for the characters, like some character depth for some of the dwarves or something, but instead they chose to use it on a lot of fan service and development of established characters. Like, great, we know Legolas is there, but can you focus on other people instead? They did it best in the second movie, in which they fleshed out most of the dwarves at some point or another. Not all, but I thought they were heading in the right direction. Then Battle happened.
But I digress. First, cut the movie into two films. Three was way too long. Next we start chopping anything I don't feel is necessary to the story. For me, in the first film, it'd be anything with Radagast the f*cking Brown. He was really, really, poorly made. I'm not entirely familiar with the actual character, but as I understand, he was a much better concept in the Tolkien world than the films, in which he was some kinda Jar Jar Binks comedic relief. Next, take out those Galadriel-Gandalf scenes (from all the movies, btw). I don't get that. I get the fan service, but really? Are they like supposed to be a thing or something? The White Council meeting was cool in the first film, but not entirely necessary. I might leave this one in, though, for the fan service. I don't entirely like the idea of them discovering Sauron here, with the blade in the meeting though, because in reality, I didn't think Sauron had a real link in the Hobbit films. Directly, at least. I get that they tried to link it to the LOTR, but come on.
I'd also throw in some more interaction with some of the dwarves, to establish their characters. They did a bit of that in them with certain parts, like Bofur's talk with Bilbo in the cave before they met the goblins. I would have liked to see a bit more of that. I understand that there's a lot of them, but...
The second film improved on the first. The dwarf characters were more fleshed out, they had personalities of their own. I knew what at least half of them were about. Kili obviously had a bit improvement here with his love interest, Tauriel. I know it wasn't in the books, but I don't mind it too much actually. Fili also had his moments here for his brother. Bofur had his, Bombur was the typical fat-guy dwarf, but he at least had an identity. Dwalin was the stubborn, Gimli-like dwarf. So yeah, big improvement. I'd still take out the scenes with Radagast the Poo. Having Legolas in here was cool, but I'd lower his role a bit. I get that he ought to have been here, but I felt adding even more to his character took away from the new one's chances to develop.
Also, I know it would reduce Ian Mckellen's role, but I'd take out all of the Dol Goldur things. I mean, I get they're trying to allude to Sauron returning and stuff, but as I understand in the actual Tolkien lore, he found out about that place and the Necromancer like a thousand years before or something, I think? I could be wrong but if I'm not, this really insults the wizard's intelligence by making him in the dark on this the entire time. Sauron doesn't have to have a large role here to be meaningful and impactful.
So the third film, just alter how it all went down. Again, take out the Dol Goldur things. Gandalf could actually be like he was in the books, making minor appearances and disappearing for long times without much explanation. I think the mysterious and ominous aspect of it would contribute to his wizardy-nature. Yes that's a word now. This probably includes taking out Galadriel, Saruman, and Elrond (even though I adore the actor) from the third film as well. I didn't like the entire battle basically. I'd redo how it all went down. The way it started felt like meeehh, OK there's a battle? Let's do it. I felt no attachment for it, not in the same way as LOTR. They did do a few cool things there, but I just felt at some point they were just having the battle there to... have a battle. At some point, I almost forgot they were having one because they cut away to Thorin, Kili, Fili and Dwalin's bit with a bit of Legolas sprinkled in, and I guess they just decided to get rid of the entire battle happening below as well.
So maybe we could divide the battle with showing scenes between that bit and the war below, and since we would have established the characters (the dwarves) in the previous films with the extra interaction I would include, we'd care about the battle and the other dwarves fighting. Or better yet, not really have them leave, but instead be all apart of the plains battle below, and that's where everything went down. I don't mind too much that the dwarves with Thorin enter later, because it made for an awesome scene, but I didn't really have anyone to connect to among the cgi dwarf-elf army, so it made the first part of it a little "whatever, they might die" for me. Also, the eagles again? Let's nooot have them be the deciding factor again. They could come in at some point, and maybe balance the tide, and help win, but please don't make them be the thing that does it again. Or at least make Beorn's role bigger, because was supposed to wreck sh*t.
Also, a few smaller aspects I would change. Bolg, son of Asog was an actual guy in the book, leading the army at the end there. I would actually have that scene in the first film where they flashback to the battle with asog and thorin becoming Thorin Oakenshield show that Asog did die, and that Bolg was there. And instead, any fights that Asog would have had with Thorin would be replaced with Bolg. That might take away from the climactic encounter on the cliff at the first film's ending, but I would actually change it so that the ending is much later on since it's two films and we chopped a lot out.
I would still keep the speech Biblo gave to Thorin about "home" in that scene though, because I really liked it, but I would include it in the real films ending, which I would probably put right after the Barrel rolling part in Mirkwood. I think i could probably easily alter it so that Thorin still has animosity to Bilbo up until he frees them from the prison there, and maybe have a final encounter with Bolg at the exit with the barrels as our last thing, if we have to have it.
So the first film would end with them looking toward the lonely mountain following the Mirkwood barrell riding scene, and just before they meet Bard.
Second film picks up right there, and we go from there to the ending. With everything we cut out about Dol Goldur, and things, it could turn out to be about 2 films approximately 3 hours long, which is fine by Peter Jackson's Tolkien standards.
TL;DR: Two films instead of 3. End the first one after Mirkwood. Cut out all of the parts with Radagast the Brown, and the Dol Goldur things with Gandalf. Take out Asog and use Bolg instead. Take out Saruman, Galadriel and Elrond from films two and three. Lower Legolas' role for the third film. Add in character development for the dwarves instead of focusing on estabished characters. Alter the battle of the five armies to include the other dwarves and don't have them separate Kili, Fili, Dwalin and Thorin from the rest of the battle. Don't make the eagles win it just by arriving again. Lower Sauron's involvement overall in the films, his presence was waaay too obvious for the premise of the first LOTR.