how to use a remote camera (webcam or Windows-usb) as my Android built-in camera(s)
I'm not sure about using a 'remote' camera, but as for a USB camera I've found a simple solution for myself as I was having a similar issue. Enable USB 2.0 and go into the Devices tab and Webcams and click on your webcam (assuming it's detected) prior to installing your operating system. This worked great for me with android x86 7.1 RC2