You are more than likely right about that.
I dont want to have acceptance and forgiveness because he didnt deserve it. He didnt do it for good. He did it for his own revenge and what he claims is his justice. Even if he is a good king, Yona can also be like that... and he can also claim the throne by not killing Il... there is a way but no, he just have to kill Yona's father and as a daughter, you wouldnt forgive that... Forgiveness wouldnt happened but I think they will have a heart to heart talk before Soowon died.
Well true forgiving someone for killing your father may be impossible but she may thank him for helping her become who she is now.
He knew he was dying but I don't think he planned to give yona the throne coz he thought yona was dead until the jae ha arc even tho it wasn't in his plans to kill yona when he killed king il I think yona will still end up dead even if she didn't witness soowoon killing her father coz soowoon's people will think of yona as an eyesore and will kill her sooner or later.
There’s something I’d like to point out that people seem to be forgetting (assuming you’re all current in the story) and that’s the fact that Soo-Won is dying of the same illness as his mother because of his blood.
What’s probably gonna happen is he’ll die and then Yona will claim the throne. They’ll probably have a touching moment too where they accept, forgive and move on leaving no hard feelings and little conflict for the throne