There's nothing wrong with OS level down-scaling? Can you show examples screenshots and videos of this? I will assume that - it will require a lot more memory

There's nothing wrong with OS level down-scaling? Can you show examples screenshots and videos of this? I will assume that - it will require a lot more memory for cached textures etc. since these are created in a virtualized pixel space - it will look more blurry and wrong, most importantly the text will be less than crisp. Apart from that, in many situations you have to scale _up_. Try any older random Windows application (that hasn't declared "DpiAwareness"), even older Windows system dialogs, on a HiDpi monitor (say 27" 4K which is about ~163dpi). They get up-scaled by the system and they look _bad_.