5 cuts?
Cloud, PacMan, Dr.Mario, Sheik, and most of all: MII! That alone should cut 3 characters in one.
If I'd had to cut more?
Jigglypuff, Corrin, Ganondorf, Dark Pit and Shulk. I would REALLY want to add Sonic here as well- but that's impossible and it would be somewhat embarrassing cause he's about the most requested character for Smash in its history
Jigglypuff and Ganondorf due to no lasting valluenof having them. Jigglypuff is extremely easy to create tho. So she's not too much of a bother. Same with Dark Pit actually.
Ganondorf is a awesome character in concept. Just the current version of him is bothersome and he's not all actually too relevant any more. His massive popularity in Zelda didn't gave him more staying power, he was shoehorned in Twilight Princess and it's his last appearance since ever. His Smash 4 and Brawl moveset are loosely based on this fight. I just rather cut him and make way for newer Zelda characters. Impa and a Champion like Daruk would be my choice. Midna and Wolf Link even would be better than current Ganondorf.
Shulk can make way for a new Xenoblade character. But he could also stay. Don't bother much with him, just don't think he's standing out much in the roster and his abilities could've been represented better.
Corrin was shoehorned as DLC. Doubt the character would've been considered at all.if not for the exact timing of Fates' release. Replace with whomever.
Also Smash should add in more 'temporary characters'. Characters not exactly meant to reapper in the next Smash. Makes all the rosters of new Smash games more exclusive. Also offers a ton of DLC options to further games.
This way, many of Pokemon's new starters, Fire Emblem one-offs, a Champion from BOTW, and other one hit wonders could make the roster without having pressure of them needing to stay relevant. Makes each Smash also far more of a generational thing.
Pichu is a good example of this. Pichu was there cause Pokemon Gold.and Silver was the last next hyped up thing. So was Ocarina of Time. So Young Link is also a good example in a way. But why stop there?
Edit: So the cuts cannot be Smash 4 newcomers?
Okay:
Ganondorf, Jigglypuff, Sheik, Dr.Mario and *sigh* Roy.
Ganondorf and Sheik could stay if Hyrule Warriors gets looked at for inspiration. But I doubt it. They overwelcomed their stay honestly. Especially with such poor represention. Their popularity couldn't save their roles in Zelda, why in Smash? Their exclusion forces a newcomer or two in the Zelda cast.
Jigglypuff is just there... Doesn't really seem necessary anymore. Her popularity also waned.
Dr.Mario doesn't bring much new. Not as popular anympre cause he's not just Mario.with a better projectile. Predicted this from the start.
Roy I had the most problems with cause his Smash 4 moveset is well fitting. But he's still not relevant unfortunately and should be on the base roster once Fire Emblem Sealed Sword Echoes gets made.
5 Smash 4 newcomer cuts are much easier tho: Cloud, PacMan, Mii Fighters, even Wii Fit Trainer can leave the building.