Thanks, Bealzebub. I gather you are some sort of flight operations personnel.
If another economy seat were available, I would take it. If a business class seat were available, I would take it. If the business class seat were given to the person of size I would accept it but would seriously consider the service commitment of the airline.
I would never become hostile although I might become immovable. When I am maltreated I do seek appropriate redress.
But I think your quote,
"From an operational point of view, we can utilize whatever resource we have available to us, and obviously we would seek to apply common sense to any given situation. However if a situation presents itself that causes an operational problem, we will always have the ability to mitigate the problem by removing it, for others to resolve at their leisure"
really sums up the actual situation.
If I complain too much about the service I receive, for example, having my limited real estate occupied substantially by a person of size, what you are really saying that this is no democracy and that airline will use all the punitive tools available to it to enforce its position even if it means that my rights and my paid ticket are ignored.
So, if I did become immovable, then not only would I be removed, I would be charged with an unwarranted crime... I've seen too many of these. How about being arrested at de-embarkation for raising a stink after being stuck on the ground for countless hours.
And, I would be arrested were I to insist that I have a proper seat before the flight began.
And without implying any malfeasance on your part, this is the essential problem with airlines these days... especially US domestic carriers... I am nothing... to be ordered about... shat upon if required for operational efficiency and charged and arrested if I complain about my treatment.