Jim_J:
So if I still want to re-purpose it for another use, I have to come up with a way to hard wire it. Whether that means de-soldering it and turning it upside down and super-gluing it onto the board (so that I then have access to the pins on the jack),... or somehow destroying the traces on the board so that I can run wires instead...
None of that can possibly work.
The Tx and RX pins of an Atmega 328 microchip are internally connected to the USART. The USART cannot be re-routed to any other pins. Read the Atmega 328 datasheet if you need confirmation.
Why not use an Arduino Mega which has 3 spare HardwareSerial ports?
...R