Postoak, the analogy doesn't work very well. Oswald's story is a strange one indeed--assuming, of course, you reject all the JFK conspiracy theorists who say he was just a patsy and someone else shot the president. And while it's possible that someone did assassinate Patton, the link to the OSS and Donovan is extremely weak: OSS no longer existed when Patton had his accident; Donovan had no apparent motive to order the hit and no longer had anyone left to order.
And JFK didn't plot to kill Diem. CIA did have contacts within the group that plotted the coup, but it was not a CIA plot, and they reported the information to DC. The decision was made at "the highest level" not to warn Diem. Somewhat similar to what happened to Allende a decade or so later in Chile.
