Hey, Cassie! How are you? Do you ever worry about characters who don't get a ton of page time, like Anush? Sometimes I wonder what they're doing while the story follows everyone else.
I've gotten a ton of questions about characters and page time (all of them from people who don't want to take page time away from Dru, Kit, Ash and Ty, but are I think hoping that it would be possible to equally feature the mains and some others and just add more pages, so this kind of addresses that) — but you are the first person to ask about Anush, so what the heck. Also I think this ties in to my previous answers about characters.
Being a main character doesn't mean the author likes you more and not being a main character doesn't mean the author likes you less — often they don't! I think people, including authors, often fall in love with side characters precisely because they have freedoms that protagonists don't. A supporting character can burst into the story with an enormous personality, make spectacularly bad decisions, say outrageous things, disappear for a hundred pages, and still remain delightful. (Not that Anush has actually done this, I think people like him because he had some fun business in TDA and he's Ty's friend but he is largely unknown.) A main character doesn't have that luxury. They're carrying the emotional weight of the novel. Readers live with their decisions, their flaws, and their growth for hundreds of pages, so they're written to sustain that journey while side characters are not. So in a way, wanting to have more of some side characters is not a bug, it's a feature.
Could you rewrite and rebuild the entire structure of a series to feature side characters as just more mains? Not without it becoming an entirely different series. Kit, Ty and Dru and Ash would all just become less significant, and all the stuff already built in for them to do would have to stop being particularly important. Kit is the Heir, but that would matter less; Ty's relationship to Livvy would matter less; Dru being who she is and having the power she does would matter less; Ash being Sebastian's son and the heir to the Seelie crown would matter less. They're all real tradeoffs.
It's also true that side characters can dip out before the consequences of being whatever kind of person they are have to be explored over 500 pages. Characters who were never written to sustain 500 pages of the consequences of their decisions can't, and the book collapses if you try. For side characters you want to see more of (Magnus, Simon) spinoff novels and short story collections are great, because those books allow for them to have protagonist business without winding up with one of those series where at the end you can no longer tell who the main characters are, and the protagonist's hamster gets a resolution the protagonist does not. (I am thinking about a very specific rodent, but I will never tell you what series, never.)
I think there is a sort of fear that since this is the end, the possibility of say, some characters having spinoff novels or short story collections or whatnot no longer exists and everything we ever want to know about them must be mashed into TWP. But that is just a recipe for turning TWP into a series in which no character is developed enough to care about, and and that is a much worse problem than wishing you saw more of some of the supporting characters, which is very normal and honestly a very positive thing. Better to want more than less or none at all, and we never do know what will happen in the future.
I suppose it's just good to remember that at a certain point, every character who isn't a protagonist is taking pages from another character. Characters people have requested page time for include: Clary, Jace, Isabelle, Simon, Alec, Magnus, Jem, Tessa, Emma, Julian, Helen, Aline, Maryse, Cristina, Mark, Kieran, Anush, Lily, Maia, Thais, Diego, Jaime, Luke, Jocelyn, Ragnor, Cameron and Paige Ashdown, Zara, Manuel, Caterina, Adaeon, the Seelie Queen, Max, Other Max, Rafe, Tavvy, and people who are very dead. Alas, they cannot all have significant page time, and that isn't even limited by the number of pages a book can be, it's limited because the ability to emotionally invest in characters is limited. At some point it's not creating a story in which more people matter, it's just creating one where no one matters.
Think of it this way: a book is not a city, it's a house. It cannot expand outward forever. (A fictional world can; a novel can't.) Every room added is a strain on the house's underlying structure, until eventually it stops being a house at all and collapses, tragically crushing all the lawn gnomes underneath.
As for what Anush is up to, he is probably enjoying not being a main character. Terrible things happen to protagonists. Anush can watch from a safe distance with a cocktail.
(Also when I say significant page time, I mean significant page time — pretty much everyone I listed gets a mention at least and some do in fact have significant roles. They just don't all have significant roles.)