Wasn't it a legal thing, at least in Europe, that when the car brakes more than 1m/s^2 (or so), that the brake lights must illuminate? Would at least make sense. Regen will be less, I guess, so lights off. Unfortunately I'm mostly _in_ the car, so, it's hard to see. But I also thought of...
Are you a step further now? I don't know if the (very old) K-Line still exists in the newer cars. I do have a VCDS from my Audi days, but I don't know if I can at least read the fault codes (will need to set up Windoes again on my MacBook just for testing this out).
Oh my, what a fantastic gold mine here! I stumbled across the XHT in the source of the Porsche Connect website, found the api.porsche.com and searched the Web, but I was expecting way less information, but definitely no samples in Python, PHP and even a command line tool. Thank you all so much...