From an engineering point of view it makes really good sense because the better you can estimate a plane's weight the better you can maximize efficiency blah blah blah. But these are humans not numbers, and it's a bit rude..
Personally I think it's a bit rude when someone is hanging over into my seat, pressed up against me and forcing me out into the aisle. I'd like to sit in 100% of my seat please.
I put some weight on over the pandemic and I do sympathise that losing weight is quite hard. But fuck if it got to the point I needed 1.5 seats, I'd either do something drastic about it (like the time I had 500 calories a day for a few months and dropped from 15 to 12.5 stone, sorry for the caveman units), or book two seats.
I will readily acknowledge that it was unsafe (I don't think it's a coincidence that's when my heriditary hair loss kicked in). I was taking a vitamin supplement and using myFitnessPal to track calories, some days I only had 300 calories but most days I had 500-600.
For me, gradual weight loss seemed unattainable. I kept trying and failing. So I just said fuck it I'm going to do something drastic to lose the weight. Of course, having willpower and losing the weight gradually is the best way to do it.
I had a woman the other day doing this. She was determined to type on her laptop despite not just her body but her elbows / arms breaching my side. After about an hour of this I got fed up, seized the moment as she got something from her bag to actually sit back in my seat for the first time. She did not like this and proceeded to stubbornly type like a t-rex with her elbow either in my guts or smashed into the crook of my arm.
Not sure what's difficult to understand for someone like that; if what they want to do involves spreading out into someone elses seat, then they have to pause the task.
Planes have a maximum weight, and it really matters where exactly in the plan that weight is. Even if it was rude, which it isn't, it can be an important safety concern
It can't be safety concern, comercial airplanes already fly with an lenormous margin of fuel, it is probably to allow the company to reduce this margin since they know the exact value and it is not an approximation that would always consider the worst case.
This will probably mean that airplanes would take off with less fuel average that can reduce the safety of the fly by almost nothing and reduce a little the cost for the company.
It should not increase the safety of the fly because it is already too high related to fuel.
If you don't understand planes, the location of the weight matters at least as much, if not more, than the amount of weight. Having a bunch of really heavy people at the back of the plan can absolutely be a safety issue. It doesn't matter if the plan isn't anywhere near the max takeoff weight.
But this is an already fixed issues, no airplane crash happened recently because a chubby guy on the first seat, the average is already being used without any risk to passengers.
Again, commercial airplanes are already too safe to any of your suggestions make an actual difference, and if it could actually make a difference Europe agencies and FAA would have already emmited alerts related to this (not an imperialist issue but they are financially attached to boeing and airbus so they usually push the standards further), and a random ass company would not be the leader of this safety standard.