"Cancun is 200 nautical miles from San Pedro, a relatively long distance that would require a specialized high speed commuter airliner."

I am a little confused regarding this statement. The cruise speed of a Cessna Caravan is 210 knots. Making the Cancun - San Pedro air time 57 minutes. The range of a Caravan is approximately 950 nautical miles although this range would dramatically reduce the payload of the aircraft; from 3200 pounds to 1500 pounds. If you were to use a Caravan to fly Cancun too San Pedro and fueled the aircraft for 300 nautical miles the payload would be 2700 pounds (this includes a 45 minute fuel reserve which is mandatory). Because of the lower payload you would have to restrict the aircraft to 11 people instead of 14. Other than the reduction of payload I cannot see the reason a Caravan could not be used for this connection.

Maybe there is something else I am not aware of.