It’s technically possible, but it would require some coding work. The main issue I can think of is that the Klipper mcu is expecting to be able to transmit messages to the host at any time (and the host is also expecting it can send messages to the mcu at any time). So, some form of “line arbitration” is needed to handle cases where more than one chip wants to send data at the same time. The usb and canbus protocols handle this at the hardware level, but as far as I know, there is no standard for this on 3 wire rs485 links.
If you can solve the line arbitration issue, then it should be possible to emulate traditional rx/tx serial over the rs485. If you look at Klipper’s usb and canbus code, both basically emulate a serial port. Indeed, the original Klipper canbus code used an external unix daemon to map the canbus interface to a unix pseudo-tty serial port, so that the Klipper host code could be used unmodified.
Maybe that helps a little,
-Kevin