Remote-controllable HDMI mixer with <=4ms of latency that can crop and position one video into another

Can you get hardware like this that can crop part of one HDMI video, and paste it over another, with position of the first video provided over some remote-control interface (e.g. serial/ethernet/usb/etc)? Video doesn't need to be resizable but that would be a nice bonus. What would be the price range for something like that?

Purpose of this would be to create a way to let you have windows from one PC overlayed on another, so you can have multiple OSs on the same screen without the drawbacks of VMs or remote desktop.