Hmm, let's see:
- Waluigi
- Paper Mario
- Dixie Kong
- Ashley
- Zelda Rep, like Impa, Midna or Ghirahim.
- Bandana Dee
- Krystal
- Pokemon Rep, whether from Gen 5, Gen 8, Gen 3, etc.
- Lyndis
- Medusa or Hades
- Elma
- Octolings
- Isaac
- Advance Wars rep(this is a bit iffy when this is mainly relying on Western popularity with no knowledge of Japanese popularity).
- Rhythm Heaven rep
- Alph......if he got the Clone/Echo Fighter treatment.
After that, it starts to get close to the barrel bottom picking, if we don't resort to picks that Sakurai was interested in, like Saki, Takamaru, Balloon Fighter, Mach Rider, etc or recent games like Ring Fit Adventure or Astral Chain. Basically, I chose the reps that either were frequently talked about/wanted, very popular like Waluigi, Isaac or Lyndis, or in the case of Dixie Kong and Rhythm Heaven, were planned.
I'm obviously not saying they are preferred(not in some people's cases) over the 3rd Parties when people would like most of the 3rd parties who share their history with Nintendo and the ones not really expected for really bring their own awesome factors and whatnot. The 3rd Parties obviously bring their flair to Smash that makes Smash more than just Nintendo games and whatnot.
But there wouldn't be a whole lot of bottom of the barrel picks in regards to Nintendo picks. The most the barrel bottom picks would be are the ones Sakurai would more likely choose himself, whereas the ones I listed are still requested or were heavily requested at one point or another. Or were planned, like Dixie or Rhythm Heaven.
And nothing states that bottom of the barrel picks can't be cool in their own right. Stuff like Custom Robo, Dillon, Sukapon, Sin & Punishment, etc are pretty cool in their own right and can bring their own uniqueness to a cast of characters of many colors, genres, styles, etc.