For a passenger who is on the aircraft when it is taxiing and wants to take another course and isnt ill by any definition its too late. The process has started of getting him from his point of embarkation to his destination.
Yup.
Unless in physical distress, he/she is to be cuffed, and deposited in the lower galley, forthwith.
Once there, shown the grub on order.
If this doesn't slow 'em down, nothing will.
Now...we did have an incident last Hajj, wherein one pax objected to their baggage being left behind (sorry dear, no space
tough luck) and...they still might be in jail in Saudi, due to the problems caused.
Saudi police marched on, malcontent pax frog-marched off...end of story.