2. This one is basically limited by what a 3 position slider (usb/bt1/bt2) can do, the firmware could do up to 5. We could offer an alternative firmware where the slider can do bt1/bt2/bt3, and USB or Bluetooth is automatically determined by whether it's plugged in or not if that helps.

5. That space is needed for the battery, since the board is too slim to place it elsewhere.