Would it be possible to write directly to /dev/i2c in Linux and spoof the messages? Not sure what the use case of this would be, but might be useful for something.
Yep definitely, I had this exact thought last night and found an example kernel module to spoof a battery, and one to read i2c messages. There's probably all kinds of cool things you can do with a kernel module to communicate between the laptop's i2c port and a microcontroller. The docking connector conveniently has an i2c port on it, maybe I'll look in to this in the future