Honestly, 2 things I feel I can add here:
1. Clones
I feel that the reason a lot of people, like myself, can see them on the chopping block is: They're lower priority. They always have been. The cuts from Melee to Brawl were mostly clones (Bar Mewtwo, poor guy) and the cuts from Brawl to Smash 4's initial roster were all either:
A. The character is a clone and are low priority to the rest of the cast: Wolf and Lucas
B. The characters mechanics don't work with the new game: Pokemon Trainer and Ice Climbers
C. The licensing for that character: Snake
2. Custom Moves
I desperately hope they cut these for the next title if it is indeed a new game. Hardly anyone cared about them, and they dropped the concept as soon as DLC became a thing. I feel like all the time put into all these custom moves could have easily given us another character, maybe 2. This also includes the Miis, granted, if they have to come back, at least make it to where they are the only characters who have customizable moves, or maybe another type of Mii (Mage maybe?) altogether. At least then, it gives them a gimmick that'll set them apart.