..., but what about the second part of my post?
Any suggestions?
Not sure that there is much we can do about which of the children should be given the role, other than via the overall promogeniture system. I suppose that, if an eldest child was born with Downs or some other problematic condition, there might be a case for skipping them for that generation.
In fact, and here's a slight tangent to the general topic of the thread, what health conditions can currently/could in the future debar an eldest child from succeeding their parent?