Has anyone tried this?
https://www.diamondbrass.com/
https://www.facebook.com/Diamantbeschichtung/
according to the manufacturer:
The layer is made of 100% synthetic diamond. Due to the nature of this surface, the bundling of lip vibrations in the mouthpiece is optimized. This makes the sound more harmonious and radiant.
Players of the Berlin Philharmoniker have done it to their mouthpiece.