USB capable microcontrollers are a buck or two in unit quantity; most of them with a USB drivers fron the manufacturer have a HID device as a standard example. It's like "Hello, World!" but for USB.
Hack? Nah. Engineer? Easily.
But the other commenter who noted that it was a BIOS limitation was right - it's not a Windows thing.
Wow, I really had no idea. That's really frustrating...
Any way to fix this? Maybe we can somehow hack the keyboards. They have an USB controller with firmware on it, right?