Your quite correct in that the B has very little electronics, only the shutter speed is electronic and for example, while you can fit a metering prism finder physically to the body, it wouldn't meter. However a motor wind doesn't necessarily have to have an electrical connection to the body to work. I don't know how the motorwind is designed to work, if it relies on contacts to the body, there aren't any so it won't work, if not then it might work (with the B that is).