As I have understand you would like to connect two physical serial ports (SP1 and SP2) to one UART in PIC?
Question which PIC you use and if there is possibility to remap pins. You could remap UART when you want and it could work. But you have another solution – software UART....
Additionally it is possible to use UART as for instance RX from SP1 and TX to SP2. And software one for rest. It is only your will
The only limit is that you will be deaf while reinitialise UARTs