Think about how arrival works:

1) plane is moving, arrives at gate, pilot hits bell and people can now get up
2) Almost everyone in the aisle seats do, they start getting down their bags
3) we wait until the GA gets the jetway to the plane and the door is opened
4) we start filing out (front to back)

For your model to work everyone who doesn't fit that profile waits for those of you who do to exit. That just isn't going to happen, I mean if you are in the first row, sure but that's already a done deal. If you are buried 2/3 of the way back in Y, there will be a whole bunch of people who are in the aisle, preparing to disembark (use the word that pleases you).

While there might be a global "optimum" sequence (I guess the function would be the one that disembarks all the passengers in the least total time), nobody in the plane has all the information necessary to figure that out. I don't know if there are a 100 people behind me in track suits who have qualified for the 100 meter dash at the Olympics and can disembark in under 11 seconds if I just stay out of the way.

I do know that all of my things are arranged and ready to roll down the aisle before the door is opened and there are few people that get down that aisle as quickly as I do. So, I optimize me, and I get out.

Alternatively, if I can't do that, for example, I was wait listed, boarded late, got a crappy window seat and had to put my bag up 4 rows behind me at the back of the plane. I'm going to relax and wait for the passengers to file out and there is no traffic moving forward before I get my bag. So, my philosophy is that I should optimize my experience as long as that does not come at the expense of inconveniencing others. I try to plan in ways that allow me to do so (get aisle seats as far forward as possible, keep my bags near me, if I have a close connection and had to stash the bag in the back, before they lock down for approach, go get it and put in under the seat in front of me...)