What if SMAUG had gotten The One Ring?

[Gordis]

Originally Posted by CAB

Gordis, I must admit I'm still not convinced that Glaurung was so different from Smaug and the other dragons.

I am not sure of all this either. The note about Glaurung posted above is very obscure. It might have been abandoned soon after being written.
"Wereworms of the Last Desert" in the Hobbit seem to be just a colorful detail, without any precise background.

I think that Tolkien first considered shape-shifting to be quite widely spread: hence Beorn and wereworms in the Hobbit, werewolves in LOTR, Radagast called "a master of shapes and changes of hue", nazgul changing shape into vultures in LOTR drafts etc. Later, when Tolkien was completing LOTR, he decided that shape-shifting was a rare thing, only possible for some self-incarnate Maiar, like First Age Sauron, or for Luthien. Sauron after his first death already lost this ability, and I doubt that Gandalf or Saruman ever could do it. Nazgul certainly not - as the LOTR now stands. With this, Tolkien may have re-thought his werewolves from original shape-shifters to spirits trapped in wolf bodies. Then the final touches to the new conception were made in Morgoth's Ring.
I think Smaug in the Hobbit was never meant to be an evil spirit in animal form, just a very clever (and malicious) animal, on par with Great Eagles, Huan, Carcharoth, Mearas etc.

Originally Posted by CAB

I wonder why, for instance, Morgoth and Sauron would imprison spirits in what seems to be a large number of wolves (werewolves) but only one dragon. Certainly dragons must have been a larger "investment", so why skimp on the spirits? Also, it is said that Bilbo was in great danger of falling under Smaug's spell. Would a mere animal be capable of putting people under spells? I'm not really sure what to think of this.

I think the "magic effort" needed "to house" a spirit depended on the strength of the creature whose body was used as target. Dragons are the most formidable of all animals, so, maybe it took a Vala to "turn" them, while Sauron could produce werewolves by hundreds.
As for Smaug's spell, I think it was not "a spell" as such, but a reference to the hypnotizing power of Dragon's eyes - a widely spread notion in folklore. Snakes produce the same effect on mice and small birds without any magic involved.