I do really have to wonder what Sakurai was thinking with making Dark Pit a clone character instead of a palette swap and two custom moves. There really isn't a good excuse for him to exist as his own character slot.
Or Dark Pit could have used the other weapons in Uprising that Pit doesn't use in SSB4. Speculation being speculation, people have started to think that Dr. Mario, Dark Pit, Lucina, Wolf Flash, Falco's "new" Bair, PK Freeze, the issue with the Ice Climbers, and whatever else are evidence that the developers ran out of time. They could have delayed the game, but didn't and Wolf and Lucas were never finished, Mewtwo might have been considered, but never finished, and the two clones and semi-clone were added to pad the game out because without them, it'd be 49 characters if you count the Mii Fighters as one character.
So, the Ice Climbers might have cost them a lot of time because they were trying to figure out them. Chrom might have been considered, but something happened and he ended up as a Final Smash with a lot of bad, insulting jokes to him, and Lucina was considered for as an alt which is stupid to say the least. She doesn't have Marth's build, except in Awakening and even then, Marth was probably taller or because nobody's seen Marth in a millennium, they don't know what he looks like, so Luci could pass off as him. Dark Pit as an alt would have been fine, but Dark Pit as a unique character would have been awesome, but nope, and Dr. Mario as an alt is kind of iffy because well, Melee.
Then you have "sources" saying Namco loved Wolf as a character or that he was Sakurai's favorite character. In terms of bias and staying neutral, Sakurai didn't want to do that, so he doesn't say who's his favorite character or if he does, he doesn't let it influence whatever character is being picked. Still, if a company, and let's say, 20 to 30 dev team members liked Wolf as a character, then why wasn't he worked on or prioritized on? You'd think that many people could persuade Sakurai or Nintendo since they're developing the game.
Then there's "alienation". Really? I swear if Ganondorf ends up as a fast moving, swashbuckling, precise, but brutal magician and trickster in Zelda Wii U and that sticks as a characterization and SSB5 still has Ganondorf as a slow, powerful Captain Falcon semi-clone... Really? And Toon Link! Where's the other iconic and unique Zelda gear he could use? And let's not get on why Zelda's design is stupid - three sweet-spot aerials. Characters evolve and while they have traits associated with them, it's not that bad to switch up something like giving Toon Link the Fire Rod or giving Zelda a rapier which is as of now, her current associated physical weapon until say, Zelda for the next console, popularizes her with pair of short swords or a magical staff.
Then there's Melee with Ganondorf's victory poses and his challenger pose suggesting he was supposed to use a sword and Wolf's "cameo" which I think was confirmed later on as Wolf being replaced by Falco because he'd "look too similar to Fox". How a wolf with an eyepatch, who's probably larger than Fox, and probably would have worn a different coat would look similar is beyond me. This might explain why Falco's air speed is ****.
Should we delve in Brawl's data dump where stuff like Toon Zelda, Roy, and Mewtwo were found? Or how Wolf's idle animation was said to resemble Fox's in the first frames before he moves to his low, battle-ready stance? Or hell, look at Wolf run and it sort of looks like Fox's stance, but in motion rather than at idle.
Whatever, speculation and all. Oh, and one last thing: Luigi wall jumping.
Ice Climbers became top 10 in Brawl 2 years later
Olimar became top 10 after several months
Now look where these 2 characters are now. Top 3 in the cast from being somewhere around mind tier. Sometimes, it's really worth it at the long run
I meant more in terms of money. So, let's say for whatever reason Diddy drops to 4 in 5 years, but in those 5 years, someone could place consistently and get a ton of cash and a ton of reputation as a 5 year veteran of SSB4.