[pessimizer]

Executive-branch head style presidents are a silly, bad idea. They only serve to give a single person a huge mandate that places them in a position to disregard the local mandates of the legislature, and at least in the US they appoint the judicial branch. So they pick the judges and can ignore the laws.

Prime ministers are representatives of the legislature, not above it, and presidents in a normal parliamentary system are like VPs in a US-style system - really just there for tiebreaking (and in that the responsibility for organizing government succession in ambiguous situations, but no real latitude.)

A monarch does nothing but make sure that a country always has race and rule by blood at the center of its constitution.