Regarding enabling additional cameras, it is is not trivial and it would require a special kernel (because it would break the existing stereo camera support). Additionally, it would require a special interposer / cable in order to use a stereo pair with another camera on a single connector (this hardware does not exist now). At this time, we do not have plans to enable this functionality. As an option, you could potentially hook up a USB camera (will require an usb expansion adapter) to supplement existing cameras (using UVC interface), but we don't provide as much support for that option since that is 3rd party hardware and software.