Opening up top and bottom (of top screen) (aka Open-matte)

I’ve been watching some VHS tapes I own with movies that have their top and bottom sides opened up from 16:9 to the 4:3 aspect ratio to fit TVs with that aspect ratio.

I’ve been imagining the top screen of 3DS games (mostly the game mentioned below) getting the open-matte treatment, where the top and bottom sides of the top screen is opened up to fit 4:3 screens.

I’m requesting to add an open-matte feature for Citra, so we can enjoy our 3DS games, including it’s non-FMV cutscenes, on 4:3 screens without cropping the left and right sides.

Here’s a comparison photo.
Game: Style Savvy - Fashion Forward

That’s nothing of Citras business in my opinion.

If you want these kind of odd modes you should use external tools to achieve them.
Setting up cropping and aspect ratios are typically features found in your OS window manager, graphics driver, your displays properties or using external video processing hardware.
However, this would happen by cutting the left and right portion of the image.

As the emulator has no control / understanding of the graphics on screen it would be very buggy / unstable to extend the screen to the top and bottom. 4:3 displays are getting rare as is so there is absolutely no point in supporting it officially as there are wouldn’t be many users.
Granted, some projects (like Dolphin) add odd projection tricks or even VR support, but I personally think those features are better kept seperated from the main project. You don’t want researched emulation / preservation with collection of hacks and game mods which are moved into the emulation core.
We don’t need any fancy split-screen splitting techniques either which is a hacky feature I consider acceptable for inclusion in emulators (because most console games used to have split screen options and upscaling half of the screen is rather straightforward).