Wasn't this a topic BMW considered either late in the 1990s or early 2000s. I am sure there was a reason it was not done back then, please do not do it now. I think it will just add confusion.
on another note:
I guess we could then have a 4M forum...haha
13 Subaru BRZ, WR Blue, 6M
09 BMW135i, Alpine White, Sport, 6M - sold
99 BMW M roadster, Estoril Blue - sold