I can't imagine the government authorities would allow this for at least two reasons:
1. safety. What if the jet needs to be evacuated because of an emergency and you're in a window seat and there is a very portly person in the middle seat who happens to be unconscious? Your normal exit path would be blocked and you can't easily climb over the seat in front of you.
2. children and infants: How would a five year old sit in one of these contraptions? How would you take a baby on board?
1. safety. What if the jet needs to be evacuated because of an emergency and you're in a window seat and there is a very portly person in the middle seat who happens to be unconscious? Your normal exit path would be blocked and you can't easily climb over the seat in front of you.
2. children and infants: How would a five year old sit in one of these contraptions? How would you take a baby on board?