Remote Start on Toyota/Lexus Hybrids - Technical Background

#1

I have a Lexus CT200h, and like all Toyota Hybrids it comes with push button start.
I have an aftermarket remote starter kit installed (dball db3), which is connected to the OBD2-accessible CAN-Bus and the “H90 Option Connector”.

The CAN Bus is used for replicating a message from the certification ecu, which handles the immobilizer/push button start and certification related functionality. This is likely very straightforward to implement with the AutoPi.
It also monitors the CAN Bus to immediately turn the car off in case a door is opened or the brake is depressed, mostly to prevent theft.

The other connection leads to (had to solder it) the “H90 Option Connector”, with 2 pins: BTX and BRX. This is some sort of bus I have not yet identified (nothing on google whatsoever) and it only connects to the main body ecu.
Using the remote starter throws some communication related fault code, so the people at directechs didn’t get everything right.
I believe that this connector is used to connect options like a factory remote starter system or the Lexus Enform (App for remote starting and other functions) system.
I suspect that only a lot of reversing and additional hardware will allow me to replicate this.
Perhaps an official kit for toyota/lexus hybrids (and other models too) would make sense because I believe that this is mostly the same with exception of a few software changes for most models.

UPDATE:
This might just be needed to get the car to turn on the relevant ECUs. Since the CAN bus is off when the vehicle is off, the remote start ecu has to have some way of turning it on. I will investigate what is electrically happening on BTX and BRX when I find some time.
This might be an even larger issue since other remote functionality cant work without a way to turn the CAN bus on. I will split this into another topic, discussing the remote control procedure when the car is off.
Sorry for having structured this post rather messy.

The main question is whether this is realistically possible to implement, and whether people are willing to help me implement it. I am an electronics engineer and anything above low level software is quite new to me.

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