Mod Request

I'm pretty new to modding, in fact I stink at it and i was wondering if there is a mod that allows you to CHOOSE the faction heir. If there isn't I have an idea. The Pope is elected by all the catholic factions, he is one of the three best choices. What if you modify it so that the same thing applies for the heir, but instead of all factions voting you do, and the best choices are the top 3 or 5 generals in your royal family. The eldest wasnt always king, When King Rufus of England died, his youngest brother Henry became king, instead of Robert, the next eldest.