Honestly... I don't think Ridley nor Ice Climbers are out of the running for this current game. I thoroughly believe Sakurai wanted to get both to work, and giving up for a deadline for the game is in no way giving up the characters fully.
I know this may not be a popular opinion, but I tend to be a person who errs on "possible." Dreamers change the world by seeing what can be done- and that is what innovative thinking is all about. It is also, seemingly, how Sakurai makes his choices. He certainly does have a creative flair for adding characters and content, and this make the game exciting... and unnecessarily shocking to many.
How I wish Meowth had gotten in initially instead of Jigglypuff... unfortunately, he may not be unique enough to be added from this point on. He wouldn't need to fight like a Pokemon, though- he never does this in the anime. He would fight like a crafty trickster, perhaps with speaking attacks, a disguise, a mecha, and...yes, coins.