Connecting linear absolute encoder with Mitsubishi FX3G

I have a request to connect linear absolute encoder with FX3G PLC, I need to offer a module or a way how to connect it.
Customer wants to use this one, on the following link:
https://www.rls.si/la11-linear-absolute-encoder

It says it has SSI, SPI, BiSS communication protocols only, how would you connect that with FX3G?

Okay, this can't be done easily, there's no module for it.

How complex would be to use RS422 module and implement SSI protocol by writing a function block that will do it?