Would Smeagol's cooperation have changed the outcome at Mt. Doom?

[Radaghast]

The Hobbit Part 1 really didn't deviate that much from the book, other than Azog's addition.

There's also Thorin being a young stud instead of an aging dwarf looking for one last chance to reclaim his kingdom. The Rock-Em Sock-em stone giants. The troll encounter was a complete wreck. Etc.

It was Part 2 and 3 that went really out there. (Though, admittedly, I liked the fight with Smaug at the end of Part 2. The idea that the dwarves had NO plan to whack the dragon in the books has always bothered me. What exactly were they hoping burglar Baggins would do, steal all the treasure one at a time? Even he admitted in the books that even without a dragon, doing so would take about a century.)

I thought that was an utter joke. Smaug unable to kill a single dwarf even when one is standing on his face? Smaug is made to look like a complete boob in this sequence. The giant gold statue. The fire that doesn't obey the laws of physics. Etc. In the book, it's even pointed out that the dwarves had no plan for the dragon. But this doesn't bother me, since the story is basically a novelized fairy tale; the thrush and the talking raven (for examples) don't seem so out of place in such a story. And it's not like the movie is not any different in this regard: the dwarves may fight Smaug and use the stupid giant gold statue to cover Smaug in gold, but this (besides being utterly ludicrous) amounts to nothing except to tick Smaug off. So how is it an improvement?

Thandril never really had a falling out with him in the books nor was it ever hinted at even.)

Of course it isn't. Legolas isn't in the book and Thranduil isn't even named.

 

[Wastrel]

Let's assume for a moment that Smeagol stays nice enough that he decided not to let the Hobbits be spider food...

Perhaps not. Gandalf says at one point, "A traitor may do good that he does not intend." I think he was speaking of Saruman.

This is part of Tolkien's "Bigger Picture." As Elrond tells Frodo, Frodo is the only one who can accomplish the destruction of the Ring. Frodo's choice of Gollum as a "guide" seems wrong to the reader and seems wrong to Sam. (We identify more with Sam than with Frodo, don't we. And yet, everything that Gollum does with his sneaky plans turns out for the best: the hidden stair to Shelob's lair is an unguarded way into Mordor; the spider-fight and the subsequent fight by the Orcs over Frodo's mithril-shirt get the hobbits over the pass; and Gollum's last treachery to get the Ring by biting off Frodo's finger results in the end of the Quest.

Then again, if Frodo was fated to destroy the Ring, maybe Gollum could have been left out entirely. He is indeed a loathsome and gangrel creature.