The problem is a part of large people start the auto victimization like some of the black people who are doing the auto victimization that are saying they are tretead bad by by white people because they are racist and here i will come with another small story. ( I am a foreign person in uk, and some of my friends are saying british people are racists, but i never feel like that even if i am foreigner most of the British people are really nice people to be around , i think if you show them respect they show you back, and i am not talking only about formal smile, even when you start to know them better, they can be genuine and trustworthy.
And second problem that is the main reason companies are still making prices in the old way is most of the people are not aware about economics of an airplane, they just sit in and never think about it, but if this people will understand how it works , and there will apear a company that can give them a benefit they will chose that company.
A benefit could be, to give you a free allowance of let's say 100kg where it's included your body, clothes that you hae and luggage.
and manny adjustment can be done, they just need to find the middle ground, all done care to not offend anybody.
It could be three sizes of seats, and evrybody will chose the seat that they need