It's gotten a lot easier than it used to be. The Glove80 is configured by downloading a firmware file and dropping it into a mounted folder. That's not very onerous at all.
That sounds terrible to me. Can you also load your old file back into the app, say, if you want to check what the existing key mappings are? Still, I don't see the point of jumping through those hoops when WebUSB isn't something that automatically happens without the user explicitly granting access to a specific device in a dialog. People are acting like a Facebook ad can just enumerate all your USB devices and turn on your microphone or something.