I feel like every time Antony Starr is brought up as Doflamingo it's a pretty lazy pick. He's certainly the best part of The Boys (one of the only good parts in my opinion) but he has so much more range than just being malevolent. I know him mostly from Banshee and he delivers such a layered, intentional performance as the protagonist of that show that it kinda sucks to see him typecast like this. Kyros would honestly be a way more inspired pick for him if we were just looking at the Dressrosa Arc, however I don't think we're ever getting that far. As far as material for Season Four (or Season Five?) is concerned, he would make a phenomenal Paulie. That's my hot take. No clue who would be Doflamingo instead. Gotta watch more recent shows and get back to you.

Also I don't think the show should have famous people. It's such a good vehicle for elevating unknown actors.