Maybe You apply the modifier to their whole provinces, or separate holdings, or personally all tribal rulers? What have You tried so far?I removed the -75% cause it seemed to have no effect. Frankly idk why they even created a tribal government type separate from feudal.
And yeah thats what I'm doing for Empires, ie kingdom-unions like the Polish-Lithuanian Commonwealth. But it is annoying that the base game is inconsistent about this.
The Empires have not been really touched upon so much since there were only ERE, HRE, Persia and Arabia in the game, despite a tone of those having been added later on.
Maybe the formation of PLC should be handled via decision? It can keep it a kingdom rank, but simultaneously move both kingdoms, as they are de jure at the moment of taking the decision into de jure PLC kingdom level title?