Sorry but that looks EXTREMELY dangers, really bad on your back, and just stupid to be honest! He can barely hold an edge! Imagine this in the surf or an area with other kiters, loosing control and that flying in the air...
Not to mention a disabled person loading this EASILY on their car how, getting it onto the beach how, into the water how, pumping the kite AND doing the lines and THEN going to enjoy a sesh... Not alone I can assure you.
Maybe as a 'kite traveling' option to go long distances , but I wouldn't be going near it!
Sorry but stupid post SCI! Common sense would put this in the kiting forum too!