How do you think the plot of Trigger Happy Havoc would have changed if, instead of Leon killing Sayaka, Mukuro killed Kyoko in Chapter One?
I struggled with this for almost a week because I hit a block near the end my mind's "Chapter 2." But here's what I do have:
Danganronpa 1 AU Scenario: Mukuro commits the first murder on Kyoko > START!
Ironically, although such an action would most likely be driven by a desire by Junko to eliminate someone she sees as the most obvious threat, I think this would probably cause the killing game to collapse faster. Which I suppose would probably give Junko a nice feeling of despair?
Unless Mukuro perceives an imminent threat to Junko's well-being, I don't think she's going to go off on her own and kill someone during the game without Junko's orders. So if this happens, it's happening because Junko requested it. And if we go by Danganronpa IF, Mukuro will need to be "tricked" into self-destructive actions... but as shown in both IF and in Danganronpa S, Mukuro isn't above turning against Junko's plans if she thinks that betrayal will better bring her sister the delicious despair she so longs for.
Basically, I'm thinking this is going to be a scenario where:
Junko asks Mukuro to eliminate Kyoko, who represents their biggest immediate threat as the Ultimate Detective. In order to get her on-board, Junko will try to engineer a scenario where they can believably frame another member of the cast...
...however, Junko will secretly be planning to throw Mukuro under the bus just like she did with the Spears of Gungnir. She's going to let there be evidence that can lead the smarter survivors (i.e. Byakuya and Makoto) to realize that "Junkuro" is the real culprit. (Because if she already betrayed Mukuro and killed her once to cause herself Despair in the canon timeline, she will logically do it again here.)
Upon realizing what's happening and before she can be executed, I wager Mukuro will start to tell the entire truth like she does to Kyoko in IF. This is the moment when she can realize that Junko is trying bring herself despair by killing her twin, so instead Mukuro will decide to bring Junko despair by betraying her ala IF and her ending in S. Junko-via-Monokuma can try to jump over and shut her up once she starts — maybe cartoonishly slapping tape across her mouth or something — but probably not until AFTER she's gotten out some pretty important information. And definitely not until after she's lost her disguise... which is already a pretty major hint for the others.
In short: I think Mukuro is going to kill Kyoko, get executed for it, and then wind up leaving enough evidence on her way out that Byakuya and Makoto and the like (I can see Celeste, Chihiro, and Sakura being useful as well) will be able to start piecing together the reality of the school and their time together much faster. The first game's canon events take place across 22-23 days. So, even if most don't believe Mukuro initially, she's going to plant enough seeds of doubt and roots for an investigation that I think the cast will be out there at least a week sooner.
Of course, there's a decent chance we'll still lose some more people along the way... so the question is: who would be next to fall after Mukuro and Kyoko, if someone else dies? Will anyone else die... ?
Here's one possible aftermath of the first Chapter that I think is logical:
With the trial's seeming reveals planting strong seeds of doubt in her even sooner, Sakura's plot development is getting accelerated. At some point in Chapter 2, Sakura will opt to begin resisting Monokuma promptly and comes forth to the others about her own role as spy/monitor two chapters sooner than she does in canon. (As it is in the mainline canon, Hina is completely forgiving but Togami is... less than accepting of her confession/apology. And for those who are now around to hear this but weren't there when it occurred in canon, I think Chihiro, Leon, Sayaka, and Taka will take it the best [in descending order from 'most accepting' to 'least accepting but still reasonably forgiving/tolerant']. But Hifumi and Celeste will land more on the Byakuya / Hagakure / Toko side of distrust.)
Depending on when in the usual Chapter 1 the first murder occurred, Sayaka may have already seen her motive video — and then been plotting out her strikes against Leon and Makoto. But once again taking a cue from IF, the stark reality of seeing blood and death in front of her shakes Sayaka out of her spiral and makes her far less inclined to make a move on anyone... but she's not exactly prepared to admit she was already plotting something, either.
I think seeing Mukuro's attempted confession AND Sakura's successful confession is going to inspire the courage in Chihiro to tell the rest of the group... something. They want to show that they have strength of will like Sakura's. They might be waffling on whether to tell them about Alter Ego's existence, which could potentially help the group, or whether to instead admit their sex/gender identity... and certainly, Chihiro's still not feeling ready to talk about both at once. But when Monokuma whips out the Chapter 2 motive, the decision is made. Chihiro comes forward with their gender/sex identity to the group as a whole, not just Mondo (although I can see Chihiro waiting for Byakuya to not be around in light of how well he in particular didn't take Sakura's admission... )
We should probably assume that Mondo and Taka are still going to bond via a sauna showdown. Which, in turn, means that Mondo's e-handbook is still going to break. No telling at this point whether this will turn out to be important at some point, but I thought it was worth mentioning.
With the "secrets" motive in play, Mondo is still on edge as he stews with dread over the idea of everyone hearing about his part in his brother's death.
...but I've mentally reviewed what I think would be the "Secret" in each envelope to the best of my knowledge, and I think there are still two other characters who might be high-strung as a result of the current motive. First up is Sayaka, whose previous admissions of having to "do things she's not proud of" to get to her level of fame is likely coming back to haunt her when Monokuma hands her an envelope threatening to reveal exactly WHAT she did.
And the other one is Hagakure; he's got crippling debt, including a hefty amount that he owes to the Yakuza. The details of that are most likely inside the envelope. Most everyone can see that he's deeply overcharging for his "predictions" and foolishly purchasing pricey items, but I don't know that he realizes how incredibly obvious his gouging is OR how futile his attempts to escape debt are in light of his deeply poor self-control. He might think he can save his reputation and still make his way out of debt if he can just somehow prevent the exact details of his debt from coming out. But... look. Hiro's just not the kind of guy who easily kills someone. No matter how high-strung he may be right now? I don't see him being driven that far. Especially given the promised fallout of "everyone else dies" even if he succeeds. Besides, even if he DID kill someone... he's gonna suck at the "getting away with it" part. :P
....and THIS is the point where I hit a block. I've given two possible suspects (and a third maybe-suspect) for a second murder after Mukuro->Kyoko, but I don't honestly know which—if any!—would make a move. Do I really think Sayaka will be down to plot a murder at this stage, given everything revealed to her? Is there any remaining event that could trigger Mondo snapping now that Chihiro's secret is already out? I don't know for sure. I'd be willing to go along with either of those given the proper framework, but I don't know which one I'd find most believable. As for murder victims, though?
If Sayaka is still going to pick a target, I think she picks Leon again OR Hiro. Because Hiro's desperation for money is easy for a rich-and-famous person like herself to exploit.
If Mondo is going to be triggered into a violent blackout-style murder by someone's words at this stage, it's probably Leon who'll do it. I can see his manner of speech and choice of words accidentally triggering something that sends him flying off the handle.
If, by some utterly bizarre course of events, it's Hiro who goes through with a murder plot? I think he targets Hifumi because he doesn't relate to him or Celeste because he doesn't like her much. Obviously, Celeste is the harder target, but it's not impossible that she might underestimate Hiro to her own detriment...
So, sadly? I think that despite him making it past the first death without going down, Leon is still in the most danger here. He's a potential victim to both of the more-likely culprits.
Regardless of whether or which murder might occur in Chapter 2, I think Chapter 3's general events are basically the endgame. Whether Monokuma gives up on the second motive or simply progresses beyond it, certain events are absolutely going to happen here.
The first is that everyone finds out about Alter Ego. With Chihiro still alive, Alter Ego will become an even more powerful tool in the investigation and unveiling of the truth.
Monokuma's third motive, the money? Though it previously triggered Celeste into murder, that ain't happening this time. Her suspicions about Monokuma and what's really going on have been raised far too much by now; she is too highly skeptical of him, I feel. And she's going to be a more key player in investigating the school's secrets as we wind down now, as well. The only person who is going to realistically be tempted by this is Hiro.
Hiro never committed any murder in DR1, but we don't really know how he felt about the third motive. It's possible that he was sorely tempted, yet Celeste just acted first. However, I think the same conclusion I came to previously in Chapter 2 still rings true here: he's not willing to cause the entire group to die, so it's not worth it for him to pursue this avenue. Besides; do we really think this guy would be able to maintain a straight-faced lie very long... ?
Once Junko/Monokuma realizes that the motives aren't working anymore, the Makoto/Byakuya/Celeste/Chihiro/Alter Ego brain trust is either about to or already has discovered that they've had their memories of the past couple years erased, and there's no spy left to manipulate into another kill, Junko going to head into triggering the endgame. Unlock the whole school, dole out the photos where her face is blocked, make them try to suss out the full truth of everything in a final showdown — ALL of that happens now, earlier than before.