Oh as I just remembered one thing that I forgot to add in the other reply - ofc I agree with most of your reasoning here. But I think that (regarding emissions)

Oh as I just remembered one thing that I forgot to add in the other reply - ofc I agree with most of your reasoning here. But I think that (regarding emissions) we need to find a better way to test/confirm this. As I believe you should be able to modify stuff you own. But I just remembered regarding certification - BMW is selling official performance/tuning kits (Sometimes called M-Performance tuning kit), where you get a whole new ECU with more power (and maybe some other parts, but nothing major for sure). And now I really wonder how is the legality of that. And also adds another point, that there are valid and reasonably safe tuning options.