So the supreme court already ruled the president cannot be held accountable for anyone they kill.
The vice president becomes the president instantly if the president dies.
What is preventing any vice president from waiting until day 1 of their parties presidency, and then murdering the president? And then instantly pardoning themself?
it’s much harder to prove because the official acts part also includes all the evidence and testimony needed to prosecute.
So if you can’t use evidence from official communication to prove that the treason happened. That makes the prosecution of presidents very difficult. It’s going to be extremely difficult for a prosecution to tell a coherent story to a jury without including any “official” acts as part of the crime.