In a comedy, a dream within a dream within a dream for ending after ending could be absolute gold, depending on how well it’s written. Though in more serious dramas, less so. (As an aside, I will use smaller dream blocks within the story to help explore a character’s unspoken fears, aspirations, etc.)
My potter story has something akin to the same dilemma, more in a couple people split off (think B-group), incommunicado (& presumed dead) until the climax. If I stuck to “A” POV, it’d get darker and darker, with a last second Deus Ex (not great). When I get back to that section, I intend to simply alternate between the two sides, muddle my way through it, somehow. However, on alternate endings, I’m thinking of having it be a sim/game with Harry & Ron played by two gamers in immersive VR… it’d be fitting to their characters.
Now, in your story, you could turn it into a two parter. You’d cover up to ending with main character feeling good about it (prelude with a few hints to the smarter character may do something), and second story would be that other character acting on the advantage and pressing forward for more chapters.