M1 is not applicable as that was a car built from 1978-1981. Did Audi have any issues in the 80's Footie?
If BMW were to make a new supercar, better believe it would be a whole different level than a parts bin car like the R8 which you can really thank Lambo for, not Audi. I wouldn't say Audi succeeded their first time around. They have yet to build a car of that level on their own instead of using an already established tried and true platform.
To answer the question, BMW does not need to build some ridiculous exotic. BMW could build a mid-engine car for 150k that would be an F430 rival that would make sense. They already have an awesome V10, that could use some more displacement, like around the Carrera GT level. Hell, even a Z8 successor with that type of motor would be great and make sense.