how else is a web based update app for a usb device supposed to work?!

It's not! It's a thing nobody in their right mind should want to do in the first place!

That question is like asking "how else is a shotgun-based dental pick supposed to work?" The things just don't go together and you shouldn't try to force them to!

Also, we already had an appropriate technology for this sort of thing (having a cheaply-made app that runs everywhere and doesn't have to be pretty): it's called "plain old fuckin' Java."