I hope you don't mind the question, because it is somewhat shippy in nature, but it's just that I trust your takes more than actual shippers in the VK fandom, and it's a hot topic right now too- anyway! Do you think Yuki will come back in any capacity? I've seen some people say her spirit will awaken to speak with Kaname for a bit, others say she's frozen in a basement waiting to be reawakened. Then there's the whole discourse of what does this say about Yuki and the story if she does come back: does it ruin her integrity, does it make a Hino a bad writer, what does it say about Kaname and Zeki, there's just so many ideas going around at the moment!
I really appreciate the ask!
Okay, this is my personal take on the Yuuki Come Back theories. In all the events we have seen of a pureblood using their magic to turn another vampire into a human, it has killed the pureblood casting the spell. Juri died doing it for Yuuki, Kaname was willing at one point to do it for Yuuki again but he decided to become the next parent metal (which I'm guessing is equivalent in power level as a spell? But then Kaname's body was preserved without his heart so I don't knooo???? THIS IS WHY I WANTED HINO TO GO OVER THE MAGIC SYSTEM MORE), and then Isaya volunteered his life to turn her human (I also remember Isaya saying that his wife died long ago turning their child human).
So just based on what little we know about the "Vampire Gene Sealing Spell", it requires the caster's life be taken to give new life to the recipient.
For me, I think it is safest to assume that Yuuki truly is dead and gone. She sacrificed her life to restore Kaname's heart and humanity. Which honestly, is really beautiful. She is his heart. For millennia, he has always hated being a vampire, and ultimately himself, and now he finally has a chance to be human and start over. And I mean the series name is "Vampire Knight Memories" not "Vampire Knight MEET YUUKI IN THE FLESH".
However it does appear that Ren has given Kaname dousing rods from Ichijou, which could possibly be used to communicate with her spirit.
I really hope it's not that he's seeing her (alive or in ghost form), but feeling her spirit. Or seeing her alive in their daughters, and himself. Helping him to understand that he doesn't need to return to his past, but that he should understand it and move forward, being grateful for the love and life she has given him.
If Yuuki comes back I don't really think it ruins her character integrity to be with Kaname, as she loved them both // YUUKI HAS TWO HANDS// and it has always been consistent in her character that she loves Kaname. I don't know how that would reflect on Hino, as I'm still trying to figure out her true intentions with this story, I think I would be a little disappointed though. I'm just so jazzed about Human!Kaname being a brand new person and living his own life for once.
And finally, as someone who loves Zero: I don't think that if Yuuki were to MAGICALLY come back and choose to be with Kaname that it would be disingenuous to Zero. She loved them both, and if Human!Kaname is healed and committed to being a good PERSON MORE POWER TO THEM. And she's not cheating on Zero, he's dead (RIP MY BOY). I think that would make ghost Zero chuckle tbh
I think Hino was a little too comfortable writing about incest and not comfortable enough with polyandry TO BE HONEST HAHAHAHA! There's just no real way around it Yuuki is for sure poly and so that validates that she has real, genuine, romantic love for two men at the same time!
I think so much of the shipping war comes from the traditional "love triangle", monogamous, "SHE HAS TO CHOOSE ONE" mentalities (*COUGHS* AND THE I̷̧̮̠̾̄̽̅Ņ̵̗͘Ç̷̪̳͐̊E̶̢͚̒S̸̼̯͈̏̀T̵͉̰̈͆͋ *COUGHS*) But if Kaname hadn't been her brother/grandpappy and we had all just accepted that Yuuki was poly and loved them both, I think we as a fandom would have been much HAPPIER AND HEALTHIER lololol but that's such a huge tangent.
But yeah.. those are my thoughts... Hino is a wild card and I just want a happy and satisfying ending.