This is more or less what we do with Solo. The NFC keys (both usb-a or usb-c) have an extra NFC chip that harvests energy and powers up the main micro controlle

This is more or less what we do with Solo. The NFC keys (both usb-a or usb-c) have an extra NFC chip that harvests energy and powers up the main micro controller. The non-NFC keys don't have that chip, so it's pretty evident by just looking at the board.