There are still characters who have not yet been cast, who would you want to see and as who??

(I'm a webtoon reader who is still reading the novel so there is much I don't yet know) 

I was looking through the cast and I noticed, yuseung shin hadn't been cast yet, neither has Seolhwa Lee or Han Suyeong or the King of Wanderers or anyone who comes up during the 5 catastrophes, so who would you like to see as these characters?