Viewport frames should have the option to add skybox reflections, bloom, color correction and blur to them since without them it all looks bad. I myself have to use images to make that possible and take the background out.
It would be amazing if we could just do this with viewports alone and not having to use another app to remove the background and all that.
And let me remind you that images are limited to 1024x1024 which is a very low resolution and will look very pixelated in-game and using multiple images would make it more complicated rather than just using a viewport.
I see no reason why this shouldn’t be added, if you find a reason then please let me know and I will try to respond to it.