It does have to do with mathematics:
- Since Melee, the dominant number of characters for each row is 9
- A new row is added in each game (64 has 2 rows, Melee has 3 rows, and Brawl has 4 rows)
- There is a 10 digit pattern on the total number of characters (64 has 12 characters, Melee has 25 characters, and Brawl has 35 characters)
- Every SSB title includes two new Pokemon reps (64 brought Pikachu and Jigglypuff, Melee brought Mewtwo and Pichu, and Brawl brought Red and Lucario)
There's no mathematical reason to why any one of those characters you mention should be in. That's ... really not up for debate. I mean, point out the mathematical reasons to why the characters you chose should be in then.
I wonder where the nearest pharmacy is. And it's still god knows who long to Foix. Dammit.