i will hire a solicitor and write down financial penalty and cancelation possibilities if any delay
I think you would probably find that MMC and/or the dealer would simply refuse to enter into a contract on that basis.
It's easy to say MMC must have known about this for a long time, but I bet resolving all the issues is not straightforward, especially not if one wants to retain the essential looks and character of the M3W.
With Euro4, you not only have to demonstrate compliance to a lot tighter set of criteria, but you also have to be able to prove that the vehicle will retain compliance for at least 20,000km
Tim H. 1986 4/4 VVTi Sport, 2002 LR Defender, 2022 Mini Cooper SE