I have had a few BMWs with run flats, probably 15 now, and agree, none have lasted more than a fortnight before ditching them.
Exception being the F11 with the latest Goodyear Eagle F1 assymetricals, genuinely couldn't tell they were run flat.
Also, my E91 330i also had them on it when I got it. I swapped over for the non run flat version and although there was a slight improvement I was expecting more.
Definitely going to go non run flat on this, I was always Michelin, but found the latest Goodyears a little more comfy, a little softer and a bit more bite when pressing on, oh and so much quieter. They are not as progressive as the Michelins when the back end starts to go, but think it might be a trade off worth it for the extra refinement.
Having said all that I bet I go Michelin again.
I do think this car would really excel with a 17" wheel, not for looks but for how much nicer it would handle. I swapped the 19s on the M3 for 18s and it transformed the car. Or even a slightly oversized tyre.
I will do some research.