Cuba Libre! - It aint just a drink.
It really would not be that difficult to whack him.
To get from one side of Havana to the other, one must pass through the "tunel" and Fidel passes through it all the time. A few clandestinly placed bombs, and a guy with an eye on his entourage could do it.
Or, we could shoot down his airplane when he goes somewhere, and blame it on the weather or something.