It's a pity you're getting downvoted, I thought it was funny.

On a serious note, presuming a significant increase in trust among all parties, wouldn't this idea radically change an ominous situation (Iran having weapons-grade plutonium laying around) into one with peaceful, mutually beneficial, trust-building cooperation between formerly antagonistic nations? Have not stranger things happened?

Iran was enriching Uranium, not producing Plutonium. Furthermore, this type of Plutonium is not what you desire for nuclear weapons material.

Iran has a plutonium reactor as well, although its exact capabilities and output are a matter of debate: http://en.wikipedia.org/wiki/IR-40

I'm skeptical that this small reactor rivaled the Uranium program. If your rush 239Pu production, you end up with a product that is very difficult to purify, raises the probability of a fizzle, and generates thermal problems for the pit.

Doesn't a lot of US nuclear power come from dismantling Russian weapons?

The needed isotope (Pu-238) is only present in small amounts in used reactor fuel.

The concern with Iran is that they might enrich uranium to the point where it is useful in a nuclear weapon (it is useful in a reactor well before this point).