Re: Errmm.. old news?
I suppose that might work - as long as the user is not in the least phased by inserting his USB drive, only to see it soon auto-magically "disconnect" -> "new USB device detected: xxxxx programming interface etc. / DFU firmware update interface" -> "disconnect" -> "new USB device detected" -> "mass storage attached" -> "new USB device detected" -> "HID keyboard" -> "Your new device is working properly". I'm not saying it's impossible, I'm saying it requires a special kind of dummy (of which there are quite a few around, granted).