I've been thinking about Dressrosa a little lately, and how it might have been improved. This isn't gonna be a cureall for its bloated nature in general, but more how to make its worst characters and subplots more satisfying. For me, the worst of Dressrosa was Rebecca and Mansherry. I want to propose tweaks that would improve the quality of these characters' subplots while changing the overall story Oda laid out for Dressrosa as little as possible.
Rebecca, short of her ridiculously sexualised design and the sexist undertones of the whole you're too pure to fight even though you've been technically doing it for years so maybe just stay out of this conflict you have enormous personal stakes in character arc was that she was set up to be something she's not. For three and a half volumes, it seemed Rebecca would be the "main" character of Dressrosa. That is to say, the character who is a local, who the Strawhats befriend, who has personal emotional stakes in whatever fighting happens next. A local capable enough to contribute in a satisfying way to the battle without being one of the crew. She was a Vivi, a Wyper, a Paulie. That was how her introduction, showing battle skill, haki, emotional stakes in Dressrosa's politics and a natural resonance with Luffy, made her seem to me, and I'm sure to many other readers. Problem was, she isn't Dressrosa's main character. That's Kyros. It's his story, not hers. He gets the final fight. He gets to actively and personally resolve his emotional baggage. He gets to strike a pose as trio with Luffy and Zoro on the volume 75 cover. Contrast: her biggest moment in the climax of the arc is when she calls for help. It can't be a coincidence that the moment the toy soldier is revealed to be Kyros is the exact point Rebecca, in spite of her experience and haki, starts losing in the colosseum, kicking off a losing streak that goes unbroken. I'm so unsatisfied with getting that from the kind of setup and introduction she had.
How to fix it? Mansherry. She sucks also, but because she's a super minor character who pulls a super important ability out of nowhere. She is set up from the start, but her heal heal powers come up basically only when the plot needs them. They come up so late in the game they feel unearned. So what do we do about that?
Rebecca should have had the heal heal fruit.
Its powers would have been set up from early on, in that case, and she might even have been able to show it by healing Luffy from a minor injury in the colosseum as a demonstration. Now the fruit's been there from the start, and is much better established for when its powers are needed to help civillians later. And what does it do for Rebecca? Well it gives her a good reason to be removed from the action, and to fight defensively. Instead of saying that for some reason she's just too inherently pure to dirty her hands with violence, Oda could have pulled an FMA style "your hands were meant for helping people, not killing."
Kyros can still fight Diamante and get his revenge. Hell, let it be a self-deprecating "this angry old soldier can't help selfishly taking vengeance all for himself and solving everything with violence," while recognising Rebecca's potential and actually telling her to leave the fight and use her powers to do some actual good for the country and for the people being hurt right now. Kyros can't let go of the past, but Rebecca needs to live in the present. She then exhausts herself putting her own strength into dandelixers or whatever, which the dwarfs could personally relay out to the people near the edge of the cage with their legendary speed. That keeps them from turning into too much of a bit part without Mansherry having the power, and resolves the plot hole of "why didn't Doflamingo or any of his officers grab any falling dandelixers when it was Mansherry flying around dropping them just anywhere?"
And when Luffy is trying to recover his strength, she would have a good reason to go looking for him, because she thinks she can personally fix him up sooner. Which is of course when she encounters Doflamingo, and things play out as normal. Maybe she gives an extra health booster to Luffy after he jumps back in. Either way, she's still been more involved throughout the final conflict, and had a much better reason to be in a position to be futility clashing with Doflamingo at the end. And that alone would have done literal wonders for her character.
But Captain M, you say, wouldn't that make the dwarfs even more of a bit part than they already were. Aren't they underdeveloped? Well yeah, but what do you want, more dwarf screentime? In an arc this busy already? Nah man, bit parts are okay, not ever character has to be worthy of literary analysis. Let them have a small (no pun intended) role as part of the island's background, tied to the old dynasty we end up trying to restore. And if they're the ones carrying Rebecca's dandelixers out to people specifically, that would mean a greater number of them in the final parts of the battle instead of just Kub and Mansherry. You could show different personalities going out to the citizens, who could have interesting reactions, having not seen or heard from the "faries" since Doflamingo came to power. Each of these a single panel affair, easily taking the place of all the shots of Mansherry flying around.
Fixing Dressrosa's pacing issues would take a ridiculous amount of restructuring and replanning the whole thing. But I think just this small change would make a huge difference to the storyline's two biggest non pacing related issues. I think it would have significantly help Rebecca's perception in the fanbase's eyes anyway.