Of course, like all such 'who-killed-JFK' or 'man-on-the-moon' type theories, you argument, however fantastical, always generates doubt.
Having been a bit of a "spotter" on the "Who killed JFK" thing I still think there are things that don't quite fit - especially the speed and accuracy attributed to Oswald on a moving vehicle with the weapon used. There were men on the moon - no question...
Was there a SEAL on the Mull?
About the same chance as Mary Jo Kopechne surviving a night with Ted Kennedy.