I also agree that Madara was just enjoying himself against Guy.
Plus, Guy wouldn't have been able to get as far as he did without the help of Kakashi, Minato, Lee, and Gaara; their efforts opened up a hole in Madara's defense of Gudōdama, and took most of what he had away from him. If it wasn't for that, Guy would have been obliterated before he even had the chance to use Night Guy.
That said, I wish Kishimoto had Guy go against Madara
before he became the Jūbi's Jinchūriki. Even if Madara was just enjoying himself, even if it was a self-sacrificing maneuver, having Guy go that fartouching the boundaries of what would essentially be the Narutoverse's equivalent to
"godhood" with a technique that all humans have the capacity to learnserved to heavily dampen the hype for Rikudō Sennin's power that had been built up until Obito's defeat.
... Also somewhat vindicated all the years of insta-win claims regarding Lee, and Guy with the Hachimon, which bothered me a bit.
Anyways, watching Guy dismantling Madara's Kanzentai Susanoō would have been much more enjoyable. Even then, Madara was an entity whose power stood above the Gokage; with Hachimon's complete release providing the power that also exceeds that, it would've been a better match-up.
I can't see Naruto putting the ninetails inside his own son.
Me neither. Not under these peaceful circumstances, anyways. I don't think he'd have to worry about them being ostracized due to his own efforts as the Kyūbi Jinchūriki, and the acceptance he gained from his peers as one. Plus, unlike him, they'd still have family to look out for them.
I could see him passing Kurama onto Bolt or Himawawri to maintain the status quo regarding the Bijū's meeting place, and they'd be the two best candidates due to them being Naruto's progeny, and inheriting the Uzumaki's strong chakra.
But, Naruto's still pretty young and will likely continue to live a long, prosperous life so long as this peaceful era continues. If not his kids, maybe his grandchildren, once he's reached a fine old age.