Ooh, I have some ideas! Ehem,
Incorporate some more aspects from Mosaic into the main story. It seems odd that an international terrorist disguised as a police officer bombing a hotel didn’t appear on the news.
Make it so that Nishijima can help rehabilitate Minene, but he does not fall in love with her. I understand that he may have done so when Minene was disguised as Natsuko, but I think it would be better if he fell in love with Natsuko and felt heartbreak when he discovered her dead body’s identity. Also, it’s one thing to ignore red flags, but it’s a whole another thing to ignore war crimes.
Give backstories to the other players. Notable examples are Takao, Kamado, Karyuudo, Bacchus, and Yomotsu. Keigo doesn’t belong in this section since his Murmur Sensei segment in the anime gives him a bit of backstory as well as his reasons to becoming a cop.
Make the future changing denoted by the diaries more prevalent and consistent. As pointed out by Kat months ago, the diaries seem to only go off whenever it’s most convenient. This is not that much of an issue until massive amounts of the changes to the future happen and the diaries don’t sound off when it happens.
If you want, take out the whole thing Yuno did. You said you wanted her to be a background character so I think it’s just to see her new game plus powers revoked for that.
If you can, adjust some of the diaries. I’ll give you liberties on how you’ll tackle this.
If you can, make it so the first meeting of the survival game happens a few days after the diary distribution rather than a few days after Takao’s death. It feels more fair to announce that everyone after acclimatizing to their new toys than after a player has kicked the bucket. Also, have it so that everyone has a chance to speak in the meeting so that Yomotsu and, by extension, Tsubaki can have an easier time recognizing the players by their voice.
Make it so that everyone can recognize each other during the meeting. Deus did such a crappy job at cloaking everyone’s identity that it’s a wonder why no one recognized who’s who from their silhouettes alone. Also, have it so that most, if not everyone, can recognize Bacchus is the 11th from the start. He is the mayor of Sakurami City yet no one recognized him! It seems ridiculous that no one knew it was him as the Eleventh from the start.
Make Takao appear more as a teacher. The animation studio had to retcon a different Math teacher because he appeared so little as a teacher in the manga.
To go off from the last point, give Takao a desire to become god. As it stands, he is the only diary holder with no discernable goal. As I see it, he appears to just be a plot device meant to jumpstart the survival aspect of the game and not a stand-alone character. It would be nice to see what goal you can give him.
Make Keigo utilize more arsenal exclusive to the police as well as actually reloading his gun during the school bombing incident and wearing new body armor during the hospital siege. It’s so jarring to see the only person using a taser in the manga to be Reisuke. Also, cut out the amusement park date he used as bait for Minene. It makes him seem careless to the wellbeing of the general public.
Remove the magic motorcycle Minene literally pulls out of nowhere for her escape from the failed bombing. It really just destroys the realism in the series.
If you want, make Minene die when she gets imprisoned by Yomotsu. She is based on Minerva, the Roman goddess of wisdom, yet she employs no strategy in order to convince Yomotsu to spare her. She has been nothing but hostile to her captor which is a good way to die.
Make Yomotsu have a limit. He may sympathize with how Minene turned out and became a religion-targeting terrorist due to the circumstances of her past, but he absolutely draws the line at killing a middle school worth of innocent children.
Give Tsubaki nuance to her character. From the canon, she appears to be too villainous, willingly wanting to subject Yuno to the horrors of rape when she hampers her plans. She can still harm Yuno, but make it so that she draws the line at that. Additionally, you can make her make her followers lob off Yuno’s arm as compensation to what Yuno did. Also, remove the kiss she did to Yuki. Not only was that nonconsensual and takes advantage of a person against their will, she has full experienced of what that’s like, it also makes her look idiotic as she has firsthand accounts of what an enraged Yuno looks and acts like.
Additionally, make it so Tsubaki have some qualms with destroying the world. Considering that seemingly the only people we see that she have good relations with in the cult are Ai and Orin, it makes a good justification to her doubting to want the world’s destruction if it means the only people with a positive relation she has will also be gone. Furthermore, if the reason before is week, have it so that Tsubaki thinks of the Omekata Temple not as a prison, but of a home that was tainted by enemies from the Unseen World. This way, it makes her seem as though she only wants to cleanse the world of sinners, but not outright destroy it.
Make a change to Karyuudo. I have a hard time understanding him sometimes and I think you’re more qualified to give him changes as you see fit.
Make Bacchus have more presence in the game. As it stands, he’s really careless with whatever happens in the game and heavily banking on the idea that no one targets him or even recognizes him. Compounding a previous point, make it so that he puppeteer the game to his advantage by pitting everyone against each other and “gently coercing” to those who are stubborn.
Make Mao less fixated on Hinata’s boobs. I understand that middle schooler can be horny, but it makes Mao seem too much of a caricature. Hell, her apprentice diary is all about Hinata’s breasts! I think it’s best if she acts a little more with tact and decorum,
Reisuke, Marco, Ai, and Kamado, and the other side characters are fine for the most part. If you have any changes to them that you see fit, feel free to do so.
So, yeah, those are the changes that I wish to see in the rewrite. I hope I don’t come off as demanding or overbearing with these, hehe. With that said, feel free to give your critiques with these ideas!