Hello! For some context: The black “borders” you see when setting a specific resolution smaller than the display are portions of the screen not actually rendered by the engine (PixiJS). Nothing can be displayed there as it’s not part of the rendered area.
What you’re describing is possible today, but you’re instead going to set your game resolution to either be adaptive, or a fixed widescreen resolution. Then you just make an image that has the center part cut out (transparent) for the “real” rendered area that you want, and you place that image on it’s own layer above everything else.
If you want finer control of this, you can set up some zoom events with math to do an inverse zoom based off the resolution of the display. But you’re going to have to work out the math to make it specifically how you want.