I know you mentioned earlier that this would have to be able to life something up and over the railing. But you could cut out a section of the railing (add hinges, make a swinging gate*) so that wouldn’t be an issue.
*With all the necessary safety precautions, of course.
You could use a “sky hook”. They are available for pickup trucks, machine shops, etc. They mount to the floor with a flat plate so that connection would need to engineered a bit so it doesn’t distort the wooden deck.