Board Thread:What If?/@comment-5674726-20140630220202/@comment-5674726-20140728173126

That'd be a whole new can of worms to open.

For the sake of the kingdom's stability, Uther would need to have his heir lined up and I wouldn't fancy his chances of getting any kind of consensus that a particular young noble was the best choice for the job, not when all of the noble families were bound to want to see one of their own chosen. Even if one was chosen, there'd be those who would lobby for him to reconsider, ie. somebody who was too young to be considered at the time of choosing could want to make a case that they are better qualified than the designated heir. The risk of assassination would be very high if getting the heir out of the way reopens the playing field for other potential heirs. There's also a risk to Uther that he would be the target of assassination attempts so he didn't get a chance to change his mind and exercise his right to designate a different heir.

With Morgana, it can be reasonably straightforward compared to the option of adopting an heir.