It seems that the best idea is to replace the current board with a new one...
Not sure if I understand. You did not mention any board in your original post.
It seems that the best idea is to replace the current board with a new one containing our own electronic circuit providing physical signals from the device (IRC, DI,...) and connect these signals to some I/O such as Arduino. This would work easily both under Windows or Raspbian, using REXDuino.
Again I'm a little bit lost here. How are encoders and digital inputs related to a USB racing wheel mentioned in your original post? Are you planning to throw away the internal board inside the racing wheel and use only the sensors from the racing wheel?