My House of Hades Theory

Hey everyone!
So... I kind of created a theory surrounding House of Hades. If we can't read it yet (which is comes out October 8th, 2013), why not come up with some crazy theories? I've gathered some information about the story, and I already read the first chapter which comes with "The Son of Sobek" (which was great!). I'd love to hear what you think in the comments!
This will contain spoilers for the Heroes of Olympus series 1-3!

As for point of views, we already have Hazel since she narrates the first chapter of HOH. Rick Riordan also said somewhere that we do get a POV from Tartarus, which means we either have a Percy POV or Annabeth POV. We also haven't heard from Jason and Frank in some time. But since Hazel is narrating, I think Frank will narrate the last one since he has a "duty" of sorts. Piper also narrated the MOA, so we might hear from Jason this time. Leo, as much as I'd love another POV, I'd rather save it for the last book (or both, please?). But then there's Nico. And here's my theory.
I'm basing this theory off of two things:
1) Rick Riordan said we see an appearance of Grover in HOH. But the main settings (I'm presuming) are Tartarus, Greece, and the Argo II. And I don't think Grover would be in Greece or the Argo II, and I sure hope he isn't in Tartarus.
2) The Romans are waging war on Camp Half-Blood. We have to be updated on what's going on there. The seven can't Iris message them every few minutes about it (especially not Percy or Annabeth cause, you know... they'll be busy fighting for their lives... hits you hard...).
My theory is that we have a POV from Nico. He's not part of the seven so he doesn't have to work on this quest. He can also shadow travel, and sure he may be weak right now, but there's always room for change! So I'm thinking that Nico will go back to Camp Half-Blood and keep us updated on the Romans vs. Greek war and see Grover there.
And that's my theory. I would love to hear what you all think to make sure that I'm not just desperate for some HOH stuff. Thanks for reading! -Kait