Oh Dan...Call me retro but I really would not mind seeing an R8 with a proper straight 5 cyl, 20 valve motor with 2,1 L displacement and force fed by a KKK the size of a trashcan lid.
The V8 and V10 are great motors but they just lack the provenance of the inline 5 and of all the motors I've heard from anyone, up to a V12, the inline 5 sounds the absolute angriest. Very, very angry.
With modern management systems 400 kW or so should not be out of the realm of possibility for such a motor IMO. It would meet emissions restrictions only underground in volcanoes but that's another story.
This will of course happen a few weeks after pigs fly and just before hell freezes over, but dreams are free so there I go.