A satisfying way to defeat Voldemort would take advantage of his genuine weaknesses - his despair in humanity, his loneliness, his arrogance, his inability to comprehend genuine compassion, his need for a worthy foe. But until the latest chapters, he had not been shown to have the weaknesses of carelessness, poor planning, or leaving a dangerous enemy armed when they are in his power.

So, up until the prophecy, Voldemort can coexist with Harry. (The reverse may not be true.) So why did Eliezer add the prophecy to the mix? Was it just to set up the eventual duel between H and V?

It seems to me that that's the place to do an Author's Saving Throw, if there is one; if people reason about V as an optimization process rather than a character, they will never be satisfied by V losing a duel because V is defined by his duel-winning property. So the only winning move is not to play, but there are satisfying ways for that to happen. (In fact, I think I might write that up in long form.)