I'm not sure the ESP8266 is a great way of accomplishing the goal of being able to know what's running by just looking at the code, unless the Espressif has suddenly opened their firmwares and toolchains. An AVR (like an arduino) would probably be better suited for the task, as the open toolchains are mature.
What would Espressif be able to do? Somehow retain the entropy it gave to the code that you used to generate the key and then send it to their servers when you reflashed with an unrelated program and connected to WiFi? That seems a bit far-fetched.
Regardless, sure, the Arduino is also a good platform to do this on. It doesn't run MicroPython, though, so I implemented my particular program on the ESP for speed/ease of development.
Don't forget the Debian bug that created weak keys from 2006 to 2008. These sorts of things happen. It's best not to attempt to disparage the possibility.
