Who was Yona supposed to marry?
It could be that question is as irrelevant as it could be...but it was mentioned in the first chapter that King Il actually intended to talk with his daughter about that issue.
So it could be more than just a guess that King Il already had someone in mind...and that could be still play a role in AnY or never again brought up again.
Candidates to marry his precious daughter...
There are people who are so sure that Hak was the one King Il wished to be the next king.
King Il was unusually fond of Hak since his teens. King Il seemed to treasure his daughter and the one to keep her save was Hak. So more or less did King Il entrust Hak with maybe the most important person in his life.
King Il would have gained:
The wind tribe people already were faithful followers of King Il.
With a marriage between the next leader of the wind tribe and his daughter he would have enforced the bond between him and his subordinates.
I think there would have been worse possibilities than Hak as king of Kouka.
The only point I think that it is less likely. I somehow would have expected for King Il to talk with Hak about that subject.
Also I would have expected for King Il to try to persuade Yona into marrying him in the first chapter, when Yona lied that she was engaged to Hak. But he didn t mention it either.
I am not sure, if King Il really was totally oblivious to the ambition Soo Jin harbored.
Soo Won was already aware of it at his coronation, so maybe King Il knew of it too.
I really would have expected that King Il would have rather given Yona to Tae Jun like he was before his “transformation” than fighting against Soo Jin.
Also Tae Jun was her husband in that “extra: What would have been if Soo Won didn t murder King Il?” Even if it was just a joke....jokes can be serious sometimes....
King Il would have gained:
He would have prevented a war and gained Soo JIn as faithful follower, since his son was the next in the line of being king.
I think it is too few...The Kai Empire would have lurked still around and the other tribes were not King Il s allies.
The only possibility I see that King Il could ensure that Kouka would be gaining a strong ally, maybe even from that country who tried to invade Kouka.
So ...I am pretty sure that would be a reason to keep his plans a secret. I cannot imagine the reaction of all tribe leaders if Kouka got to be a vassal state of Kai. Cementing their bond maybe with a marriage...
Nothing of this sort was ever mentioned. But I still deem it a very fine possibility for King Il s self-loathing.