Alternatively they can group all the morbidly obese in the same rows and let them sort it out amongst themselves.  I wish it was that simple. Expecially on smaller aircrafts they need to balance the people on board to ensure a safe flight. It may be a problem to have a row full of deathfats. Maybe 4 rows can work, 2 in the front and 2 in the back may works, but they need to know in advance.