Do you have an example of said tuneable Fn2 ECU? Cause if its a Piggyback ECU then usually might possibly work as long as it supports any K20 [Don't see why it wouldn't unless there are things on the K20Z compared to the K20A such as Fly-By-Wire, MAP v MAF then you have issues], these issues can be worked around if you have the correct equipment.

Why the need to stick with Euro-R/Euro-R parts specifically though? A well planned and executed plan with aftermarket parts would yield better results. You might want check the difference between the JDM K20As and your K20Z. Cause there are differences that tuning and bolt on parts alone can't breach the gap.