If it was 1920 wide of any height of at least 1080, I can now display 1080p media with no scaling (its really hard to get players to not scale while full-screening, and scaling from 1920 wide to 2560 wide can never work well, even with high quality Jinc or even cutting edge machine learning scalers); but also, just streaming desktops that are already on standard monitors.

You don't need a smaller monitor to display without scaling. You can simply view the video in a 1920x1080 window.

But I don't want it in a window, I want it centered in my screen with no scaling applied without having to do any shenanigans on the laptop's side.

power consumption, other then that i also dont see it. i have laptops with 16:9 16:10 and 3:2. I find the 16:9 worse.

Maybe use MacBook only for watching videos?