Even tho a 7M is not my motor of choice, I would have to kindly disagree with you on your opinion/comment.
Depending on what you do with the car will dictate what is going to happen to the motor besides all the up keep needed.
If its just a daily driver a OEM headgasket is okay to use, but this is SON and it is a build for something more than just a DD.
I would say with 100% confidence if he puts a metal headgasket he is golden.
I did a complete head job on a 7M so its brand new again and to this day there is NO issues!