ummm... yeah, i think that would fail as an R8 killer. here's why:
R8 = 4.2L V8 (414hp) or 5.2L V10 (518hp)
Z10 = 3.0L I-6 (400hp)
in order to "kill" the R8, you must be able to beat it at its own game. right now, if the idea is a nice competitor to the entry-level R8, this idea can do it. Kill the R8? no way.
however, this 3.XL I-6 would make a nice addition to the next M3!
'12 X3 XDrive 35i
'13 335i MSport
Past - '06 330xi, '07 X3 3.0si, '09 328i