I hear what you say....
Do you not think that it is the cylinder head that makes the biggest difference to defining what 'special' is?
I'm pretty sure the S55 will have a all new cylinder head, pistons and conrods. Most likely Crankshaft too. For sure the Turbo arrangement will be unique, and according to the GURU above BMW M will ensure it has NO lag as that is what people want
The N55 of course has plenty of lag.