All the viable choices from the first two gens kinda suck ass.

Sandslash would kinda fit but no one would ever vote that in. No one would vote Golem in either. Picrel would be the only two bipedal choices out there.

>But quadripedal is possible too
Sounds like a mess to program, but maybe Eevee being a Pika clone. Neutral-B would be Palutena's Autoreticle (Swift), and Down-B would be Pikachu's Skull Bash used in later games.