You are correct in that you can address up to 256 devices using a byte variable and 65,535 using a word variable. The problem is how to program the device id? That is what I believe he meant by "short of reprogramming". You could program it though so you could change it in software. I would assign a default value that doesn't get used for anything else but installing new devices. For example use id 0 for new devices only. This allows you to put a new device on without interfering with other devices prior to setting the device id.