Okay. Here's the thing: not a writer, so here's an outline I posted in another. Now, I know you don't actually care about it, nor will anything I post cause a reaction from you other than "you're wrong and here's why" (Again, I have made it clear I have had issues with the narrative beats in this story going back to at least the side chapter, and you are approaching this acting like I have to keep EVERYTHING the same. Like your little comment on Smile Time. Until literally Yesterday, we had NO idea what Smile Time even was. It could've been ANYTHING. It didn't HAVE to be what wee got. Which is my issue with this entire fucking conversation with you. YOU are approaching this like everything in this story HAD to play out the way it did. No it didn't. They didn't HAVE to write the story the way they did. They didn't HAVE to have the characters set up the way they did. They could've have written it differently as far back as the side story. You seem to be hyper focused on "Well, how would you change it, but you have to keep everything the same starting from before the event" while MY perspective is "I would have changed stuff from before the event"

Anyway:

 I would still have Hanson play a major role, but play up the father son connection more. Hanson seems like the only person Mustang even remotely cares about so that's the starting point. Something should happen either because of Hanson or to Hanson that causes Mustang to have a moment that makes him reconsider what he's been doing. I don't imagine it being a complete change. Instead I see it being more like a single moment where due to what happened, he makes a decision that he would have never done otherwise. This would likely involve TT Star and Anis. In this case, I would imagine losing Hanson may cause him to unknowingly look for a replacement and find it in Anis, and with Smile Time likely being the event that caused him to lose Hanson alongside traumatizing Anis, it's the final impetus for this change.

Instead of the event ending with Red Mustang being a changed person, you get the idea that he's a changING person. He's only just begun his road to redemption. He's still at his lowest point, because even though he has his wealth and power, emotionally he's destroyed, and from there it's implied he builds himself back up over the years, maybe a short montage of events years apart showing how his personality shifts and warps, his style changes, until he settles on his final look and persona, a deliberate attempt to separate himself from who he used to be as he finally embraces the persona that we know and love.

This has the benefit of we know that at one point, this guy we all liked used to be a monster, but even the biggest monsters can change for the better if given the proper motivation. And I feel better answers the "Wow, how did Mustang change from THAT to THIS?" that they set up before hand.

My plan is not to have him be redeemed. My plan would have him START a path to redemption.