Depends on what is provided. Will the flight model be updated along with the exterior model?
Also, in reality the systems are not totally different based on systems function, as they are the same from what I understand from the -300ER based on the data I have. The flight deck differences can also in theory be pulled from the 777 expansion that you also did.
Major differences can be referenced here:
https://www.boeing.com/commercial/aeromagazine/aero_03/textonly/ps01txt.html