Unfortunately it's going to take a number of lawsuits for there to any change.   I'm dreaming of the day I have my kneecaps fractured from the seat in front of me reclining (I'm 6'2"/1.8m tall, so my knees are usually pressed against the seat in front of me) and I sue the airline over the matter, ideally forcing them to illustrate what my ticket purchases in terms of area/cubic space, how they double sell the space directly behind seats, and that I was injured by the seat performing to it's designed functionality. Something like that would easily be applied to the obese sitting and spilling situations.  But with obesity becoming the norm, it's going to be difficult for changes to be made.