There's a ton of low-latency proxy hardware meant for cheating that does exactly that, out of the box, for those too lazy to do it themselves on any devboard. It's not an excuse for closed source mouse firmware

it's hardly difficult to do that already. Like a Raspberry Pi Pico can be turned into a HID mouse rather easily: https://www.instructables.com/Raspberry-Pi-Pico-As-HID-Mouse...

and yes, hdmi/displayport capture -> ML object detection -> fake HID mouse to cheat is absolutely already a thing.

It's already being done. The fanciest game hacks use a custom PCI card to DMA game memory, read it on another computer, where it can do wallhacks and such.

But also, the second computer can drive a virtual mouse and keyboard which is connected to the 'legit' PC to even aim/move/shoot for you.