I've noticed, that, in general, nobody seems to be able to agree which button is "A", and which button is "B". This leads to some annoyances. One cart, X is jump, O is attack or etc. You get used to that, and then you go to another, and they chose O for jump instead.

It would be nice to have a simple way of swapping the buttons around, perhaps as an item in the pause menu? Some carts already have their own, though, so that may cause some confusion. Maybe make it disabled by default? It'd also be nice to be able to have it remember if you chose to swap buttons or not per-cart, so that you don't have to every time you start it up.

If you're on a keyboard, a quick fix I've used for years is that [z] and [c] both map to the O key. If you don't like the order of the X and O buttons, just move your fingers over by one.

Agreed that we need better key mapping in general, though. Even the notorious walled garden that is Nintendo recently added hardware support for key bindings to the Switch OS.

+1 to this feature request

it would be really cool if it would even swap the visible button glyphs so that on-screen prompts "feel" correct based on your preferred layout and the association you have in your brain between symbol and physical position! this would not work well in some carts which print the keyboard letters "Z" or "X" though, but I would say that's bad accessibility practice anyway because it assumes the user is using the default mappings and is using a keyboard

I disagree, O is B and X is A.
 
 

 
 
Now the problem is, are we talking nintendo BA or xbox AB :D

Fully agree, @Spaz48 and @kittenm4ster. Despite the fact this was requested years ago, it's still a problem. In fact I posted something recently about this.

https://www.lexaloffle.com/bbs/?tid=45728