Hmm, what if Finn recognized the patrolling stormtrooper that Lando shoots? The scene could play out slightly different so they could have a longer interaction. Then, while they’re on their way to Kijimi, Finn and Rey could be exploring/repairing Ochi’s ship when he has that brief PTSD moment.

This may too radical of changes, but I just wanted to throw these ideas out. If you were to go with the idea of Finn starting a revolt on the Star Destroyer, I also think it would be interesting if you had some scenes play out differently to where Hux survived until the final battle.

First of all, I would remove the idea that Palpatine has his own soldiers. All he has are his Sith cultists/loyalists, and his large leftover fleet from the days of the Empire. They need the First Order’s army to man it. I would also change the red Sith Troopers into “Royal Troopers”, a legion of First Order stormtroopers that are meant to defend the Supreme Leader, whoever it may be.
Pryde could be present at Poe and Finn’s execution, and Hux takes this opportunity to save them, as well as killing Pryde.
The scene between Palpatine and Pryde will now be between Palpatine and Hux, and he orders Hux to come to Exegol to use his army to man the fleet. He also could call Hux, “Supreme Leader”. Plotting a coup seemed like an obvious direction after the way Hux looked at Kylo at the end of TLJ, so I think it would be more satisfying to pay his story off.
You give Pryde’s role in the final battle to the newly named Supreme Leader Hux.
While Finn and Jannah are on their way to destroy the signal tower on the destroyer, Finn gets the idea to instead hack into the signal tower and transmit a call of rebellion to the stormtroopers on all of the Star Destroyers.
This would be a brand new scene, but you could write a quick montage of troopers taking their helmets off on various destroyers and turning on the officers, including Hux’s destroyer.
Hux could hear over the comms, or see on the ship’s surface, that troopers are rebelling, so Hux’s orders the ship to self destruct before the bridge is overrun and Hux is killed by his own men. I just think if you’re going to have stormtroopers rebel, it would be much more satisfying if Hux was the one reaping what he sowed. ( This whole change also allows you to change the awkward interaction between Finn and Rose where he basically tells her he’s gonna sacrifice himself, which totally goes against her message to Finn in TLJ.)
Transports full of troopers could be described escaping the destroyers during the resolution of the battle.
During the celebration montage at the Resistance base, you could replace the awkward Lando/Jannah interaction with Jannah greeting the newly defected troopers. You could have an interaction like this:

Jannah: I’m Jannah. What’s your name?

Stormtrooper: TZ-359

Jannah: No, your real name.

Stormtrooper: I don’t know…

Jannah: Well, let’s find out.

While there definitely would be some brand new tidbits with the stormtrooper rebellion stuff, I feel like a lot of this would allow you to keep the same scenes, technically, but you’re just swapping out characters and dialogue.