I have a simple but great solution for this agenda since it seems that it has no real drawback and that aggro decks (mainly stark, GJ and Targ) are getting too easy draw thus overpowering the meta. Rather than restrict it or ban it or make it unplayable, let's make it Baratheon house only.
It could see use in some lord rush or asshai decks and have a real drawback in the form of reducing chances of finding that Stannis or Melisandre that you need badly.
Problem solved. What do you think FFG ?