EU5 Vassals

I am really bummed about this, and yet I don't know if it's a feature or not or if it will be. You know in CK3, the whole vassal feature? Duchies, earldoms, counties are all part of a kingdom, but are granted to independent rulers? I think this is a must have in eu5, it starts earlier, you've got the hundred years war, the war of the roses, these are all historical events where this feature is incredibly important for about the first 200 years of the game's start date. If this never gets added, even as a DLC, will it be moddable, or is this just not the way a game like EU5 can run?