There will have to be improvements to deep-fake technology that allow the hair to be changed as well as the size and structure of the face. The Rock’s head appears smaller in proportion to his body than Schwarzenegger, as well as having a different shaped skull. The ears are also an issue.
The “silhouette” aka outline or perimeter of the face and skull stay the same, so Dwyane Johnson’s cheekbones and basic facial structure helped sell the Arnold look.
It’s interesting how deep-fakes allow you to contrast personalities between individuals. Even with Schwarzenegger’s face, Johnson quickly becomes someone other than Arnold, if not full Dwayne Jackson.