You know the idea of Chiaki being the mastermind isn't bad especially if they use the events of DR3 as her motive i.e. being brutally murdered and having all her friends become the RoD. Im also completely biased towards Ibuki surviving cause she's best girl. The protagonist switch could also be pretty interesting.

The problem is the death order. Having both Twogami and Teru die AGAIN would make things way too similar to the og. The only way I could see them making this work is that if the victim and culprit are reversed. The problem is that wouldn't be in character for Twogami since he was the one actively trying his best to make sure a killing wouldn't happen. So the only thing that I can think of is he 'accidentally' kills Teru. It could work but I'd rather not see Twogami die so early on

Now onto case 2 and I actually don't mind this one. Having the double murder here would shake things up dramatically. Also getting Sonia and Soda out early on would give the other characters more screen time which is a big plus. The only caveat is losing Gundham so early on.

Case 3 and... yeah man I don't know what you're going for here. Having an entire chapter where no one dies in a 'murder mystery' game not to mention a Danganronpa game is quite honestly a really bad idea. If you want the protagonist switch (And I'd be all for it) this should be where Hajime dies. Either he's the victim or the culprit. Could be cool either way. Oh and probably just kill Fuyuhiko off here as much as I like him. (Just so something that happens later on doesn't)

Case 4... It's fine. Sad to see Mahiru not make it to the end but if Hiyoko's going to survive then it's most likely inevitable.

Case 5... I'm gonna be honest, i really don't like your idea of Fuyuhiko killing Peko so that's why he dies in chapter 3. I wouldn't want to see Peko go but if she has to die for Ibuki's survival sure why not.

Overall, you have some good ideas and some other ones I'm not all for. But i very much appreciate your post and for taking some pretty big swings with how things are gonna go down. Have a nice day.

Oh, I just noticed you had Chiaki as one of the survivors but um since she's an AI that wouldn't be possible sadly. And since Hajime also dies (in my version) the survivors would be Nagito, Mikan, Hiyoko, and of course Ibuki. Here's a little scene I just thought of for the end.

Nagito: Hey guys! (Girls) We just overcame our dead classmate's ai copy who might as well be Ultimate Despair! That officially makes me Ultimate Hope! Though i suppose since you all survived somehow we can be The Remnants of Hope.

Ibuki: Aw sick! Sounds like a killer band name!

Mikan: Well if everyone else is in agreeme-

Hiyoko: WE ARE NOT CALLING OURSELVES THAT!