RX with internal pullup

Is it possible to use the internal pullup from D1 while it is being used as UART? I wan’t to place a MOSFET (P-channel enhancement type) to it to transfer from ±12V to TTL on the UART pins.

It’s just an idea and I want too check if it’s possible too use MOSFET’s instead of BJT’s to reduce space on the PCB.

The wire with the via (grean circle) is the RXBUS, most left the ground and the ones directly to IC1 TX and RX in that order.

Thanx in advance