Modding Personal Unions and Client States

I'm trying to mod the game so that the subject-overlord relations in the game are more accurate as well as some other things.I want to do this by g.e. turning France's "vassals" during the Napoleonic era into client states and turning the alliance between Spain and Austria at the time of Charles V into an actual personal union. But I can't find anywhere how you do this through modding. Anybody have any information on this? via /r/EU4mods http://ift.tt/2scwtsL