I don't think SJ and Hwi would work because there are major besties vibes between them. Even their date did not feel like a date. Once SJ reveals it, it's gonna be chaos but they def not going to get together. The directors just want drama and us to believe that there might be 4 winning couples out of this.
There might be disagreements about the ending but let's be honest Yiheon can now leave with the assurance that his life which he threw away can be lived like that and DeukPal deserved to live the life he lost while he tried to save him. So I think I'm very much satisfied with the ending.