Seems rather unlikely to me, especially since Cuba's middleman was meeting with U.S. officials in France at the time of the JFK assassination to work out details of a mutual agreement for peaceful coexistance.

Not only that, but Oswald was practically thrown out by Russia and denied by Cuba, if I recall, so it doesn't seem likely that the Cubans would make an organized effort to use him, especially if the United States had tied them to Oswald.

As someone who has researched the JFK assassination quite a bit (currently reading the latest book "Ultimate Sacrifice" by Hartman), there is no doubt that the Kennedys both hated Castro, and that they had used the mob to attempt assassinations against him. Whether or not the Cubans "struck back" (as books like Gus Russo's "Live By the Sword" claim) with enough power is one of many theories that still are open to discussion.

For starters, DC, regarding Oswald/Ruby, I'd read Peter Dale Scott's "Deep Politics and the Death of JFK," which delves into the history of Ruby quite profusely. Also, it explores James Angleton, CIA spyhunter who many believe played a role in the orchestration of Kennedy's murder.