PIC18F25Q43 serial combiner - possible?

[richard]

a bit more detail on the streams would not go astray , i expect the streams are not synchronized in any way, don't have fixed lengths, the length is not embedded in the stream and that there is no discernable end of tx char and for full inconvenience there is no flow control. you will need a good strategy not to get mixed messages, bit banging serial in or out will be near impossible, q43 looks good to me.
in the olden days 90's we had these things called print sharers . 8 pc's 1 serial printer they managed ok somehow