That will be it.The whole reason why the line of Japanese Emperors remains unbroken,apart from the whole 'divine' thing was because no one wants to know the consequences.As long as no body tries to open the pandora's box and show that they can get away with it,the political strongman of the time will try to rule as regent/shogun/prime minister/Chancellor/Mayor of the Palace.
If Simon Montfort's rule during Henry III had lasted longer, could that be something in this vein - getting a parliament-supported leader while the king is powerless. Trouble is how to make it lasting over several generations.