Audi has the best naming convention..."S" for a more-performance oriented car and "RS" for more hard-core.
Mercedes has the AMG and AMG Black Series.
At the risk of copying Audi again, BMW should consider using "S" for something like the current m235i....an S235i
And keep "M" for pure M cars...
But honestly, I don't care that much. I don't mind admitting to my friends that my m235i is not a pure M car...I'm ok telling them that I'll get the real thing in about 3 years
But no. Please, no "2M"...it's already confusing enough. "1M" was a one-off limited car that couldn't re-use the "M1" name for reasons we understand.