What could happen is that an eagle flies over the Lonely Mountains and stops for Bilbo to tell him to warn the Lake-men. The eagle, already revealed after the battle with the wargs at the Misty Mountains to be able to talk, then warns Bard. This does not differ to far from the canonical story and provides a segway into the arrival of the eagles as the Battle of Five Armies.
Another possibility would be that when Bilbo, Gandalf, and the Dwarves are ambushed by wargs at the Misty Mountains, Gandalf calls for help from the eagles via the small moth creature used for the same purpose in The Lord of the Rings. Then, when Bilbo learns of Smaug's weakness, he recognizes the moth and tells the story to it, which then flies away to warn Bard who can understand it in a similar way Gandalf does. This also provides a segway for the eagles to arrive at the battle.
What could happen is that an eagle flies over the Lonely Mountains and stops for Bilbo to tell him to warn the Lake-men. The eagle, already revealed after the battle with the wargs at the Misty Mountains to be able to talk, then warns Bard. This does not differ to far from the canonical story and provides a segway into the arrival of the eagles as the Battle of Five Armies.
Another possibility would be that when Bilbo, Gandalf, and the Dwarves are ambushed by wargs at the Misty Mountains, Gandalf calls for help from the eagles via the small moth creature used for the same purpose in The Lord of the Rings. Then, when Bilbo learns of Smaug's weakness, he recognizes the moth and tells the story to it, which then flies away to warn Bard who can understand it in a similar way Gandalf does. This also provides a segway for the eagles to arrive at the battle.
Although it wasn't present in the books, it would be interesting if there was some sort of development between Smaug and the Ruling Ring. The one major point when describing Smaug is his greed. I don't know how it would work exactly, but it would give Smaug a reason to develop a more clear relationship with Bilbo, which, in turn, would give the plot more 3-dimensionality.
An interesting scene that would foreshadow the Ring would be that the Ring slips from Bilbo's hand at his encounter with Smaug, and Smaug tries to burn Bilbo with his fire-breath. Bilbo would jump out of the way, but the Ring would be caught in the blast and remained unharmed and then, although Bilbo doesn't get the chance to see it, there is a shot of the fiery inscriptions appearing on the ring.
Another possibility would be that when Bilbo, Gandalf, and the Dwarves are ambushed by wargs at the Misty Mountains, Gandalf calls for help from the eagles via the small moth creature used for the same purpose in The Lord of the Rings. Then, when Bilbo learns of Smaug's weakness, he recognizes the moth and tells the story to it, which then flies away to warn Bard who can understand it in a similar way Gandalf does. This also provides a segway for the eagles to arrive at the battle.
Another possibility would be that when Bilbo, Gandalf, and the Dwarves are ambushed by wargs at the Misty Mountains, Gandalf calls for help from the eagles via the small moth creature used for the same purpose in The Lord of the Rings. Then, when Bilbo learns of Smaug's weakness, he recognizes the moth and tells the story to it, which then flies away to warn Bard who can understand it in a similar way Gandalf does. This also provides a segway for the eagles to arrive at the battle.
An interesting scene that would foreshadow the Ring would be that the Ring slips from Bilbo's hand at his encounter with Smaug, and Smaug tries to burn Bilbo with his fire-breath. Bilbo would jump out of the way, but the Ring would be caught in the blast and remained unharmed and then, although Bilbo doesn't get the chance to see it, there is a shot of the fiery inscriptions appearing on the ring.