Awesome that you didnt fry your headgasket. What's not awesome is peoples MISGUIDED ASSUMPTIONS THAT BECAUSE A THERMOSTAT IS METAL (VS PLASTIC) THAT IT'S OMGGG BETTER than BMW's solution (OE parts)
There's NOTHING wrong with an OE/OEM thermostat--in fact it's the best g-damned option there is. Same goes for the water pump. So what they dont last 200k miles--you shouldn't be running your car that long without a cooling refresh anyway.
Quit it with the ALUMINUM THIS ALUMINUM THAT. Just buy the right OE or OEM parts and be done with it.