I thought I replied to this once already?
Maybe I wrote something and got sidetracked before posting...
Anyway, I've been looking at i2c for communicating with several arduinos.
There are several i2C devices already supported in Tasmota. I thought about emulating one of them with an arduino.
And then I saw how easy it is to send/receive serial messages instead.
I don't know if this helps in your use case, but I'm now thinking of having an Arduino digest the serial commands.
It will run a program that uses i2c to read or write several *other* arduinos then.
If your remote device has a serial port and you're only talking to one device, I think you should really investigate using serial instead of i2c.
I'm trying to add 4 analog moisture sensors and 4 servos to one esp8266.
It already reads an analog tank level sensor, operates a valve, and cycles a pump.
I've simply run out of pins. Even if I emulate existing i2c devices, I can't add multiples of them in the firmware.
No support for more than one address of the same device type, near as I can tell.