What it seems you are describing is a multiplexer - something like a 74HC_HCT4052 . This will allow selection two banks of four unique *analog * or digital signals and route them to/from a single pair of pins. Which of the four signals is connected to the single pin is controlled by two address pins.
If the Arduino controls the address pins you can choose, under program control, which xmit/rcv signal pair is active.