If they go down that route, they definitely need it to be not some "it was all fake" thing; at most, it needs to be that he is an accidental chessmaster, perhaps spreading his influence to the outside world through the Ultimate Imposter. That, or he has hyper awareness of his surroundings, which results in his work being influenced by past events.
On the other hand, it COULD be that all of Danganronpa was just us seeing the finished product of Mitarai's work - and Mitarai is just a self-insert character. Mitarai is a character consumed by both hope and despair, which is why his creations (Junko, Mukuro, and Nagito) are able to corrupt his vision. He is such a good animator that his work just flies onto the page. He looks at Makoto with such reverence because his creation is the kind of person that he himself would want to become someday, but is never able to become. By the time the Future arc comes along, he has basically lost all control of his work. Juzo attacks him and the killing game began without any ability to do anything about it. Thus, when he asks Kyoko what she thinks, what kind of person would do such a thing, he's inviting her to comment on him - the person who, ultimately, is responsible for creating both Ultimate Hope and Ultimate Despair, and thus, why Kyoko is constantly suspicious of him. Asking him what his NG is, suggesting that he knows something, etc. In reality, he is the mastermind