Why not have a diverse selection of characters from different FIELDS.
Not like SSBB, but more like:
Long Range Character with weak close combat moves
Short Range Character with weak projectiles
Spammy Character with weak specials
Dodgy character with weak everything
Weak character with kick ass specials
and so on.
As not to have all characters perfected after one. As in, 'I have perfected Peach, but she plays the same as most of the other characters so now I have them mastered!'
Catch my drift?
1. Mario-Short range character with mid-weak projectiles (fireball).
2. Sonic-A fast moving character with mid strength moves but low health.
3. Yoshi-A mid speed character with some powerful and weak close combat moves, but no projectiles (all rounder).
4. Cless-I honestly don't know...
5. Zero-A mid-fast moving character with mid-strong projectiles and mid-strong close combat moves, but low health.
6. Korrin-I honestly don't know here either...
7. Mega Man-A mid speed character with powerful projectiles and mid strong close combat moves, but low health.
8. Kirby-A low speed character with an array of different abilities, supplying strong, mid and weak projectiles and close combat moves. A more 'strategic' character to use correctly.
9. Link-A wide array of mid projectiles paired with strong close combat moves makes for a kick ass man.
As for a 10th character, why not a character with strong close combat moves, little to no projectiles, a kick ass special, high health, but INCREDIBLY slow?
Bowser, Donkey Kong or a third party guy could fit this bill.