What of opera as conspiracy theory? How about a JFK assassination opera? Was Lee Harvey Oswald really a double agent for the CIA? Maybe John Adams should do an opera with this as the subject. It would have actual characters, unlike most of his stuff, though the story isn't about love.
Of course, the problem with a JFK assassination plot is that there are too many options. I might go for a murder by the CIA plot. My favorite has always been the murder by Castro theory. That would be very amusing.