The reality is Com Day moves are so good for starters I don’t see them giving them up in PVP.
Which means 2nd Move is about options and coverages.
Blastoise is an odd one, while Aura Sphere is going to make it a beast against Registeel, lacking Ice Beam is going to hurt against Giratinas. In another words, adding a Coverage Move there doesn’t feel like a big deal because it already had one.
I only looked for a couple, but the only one that stood out to me was Dragontail on Meganium. Anyone think of any others that they could add to a Starter from its movepool that would change the Pokemon?