Sauron versus Aragorn

[Galendor]

I know how it would have gone: Aragorn and Sauron would fight while the armies watched, ordered to stay out of the fight. Aragorn would get knocked around fiercely during the fight (more than a mortal man could endure and yet live). But in the end he would summon the strength of the Numenor and heroically behead Sauron.

He would turn in exhausted triumph towards his army, but behind him we would see Sauron pick up his head and place it back on his neck. Gandalf would despair and look at the ground, knowing that Sauron cannot be killed while the Ring still exists (he would probably mutter something to this effect so that the audience understands this subtlety).

Sauron and Aragorn would fight again and this time it would go badly for the exhausted Aragorn. Finally, he would be on his knees and Sauron would pause to gloat before killing him. Flash to the events on Mount Doom, where Frodo is defeated by the will of the Ring (everything is going just bad, bad, bad). Then Smeagol attacks, and the Ring + Smeagol fall into the fires, etc.

Flash back to Sauron, who bursts into flame or explodes or whatever just before killing Aragorn. Aragorn, Gandalf et al. realize that Frodo was successful and the rest of the movie proceeds. This way both Aragorn AND Frodo get to be heroic and "defeat" Sauron in their own way.