You know, I've been thinking that if Ridley is playable, he will probably be given an entirely new design for Smash 4. The reason I think this is because Zero Suit Samus was given a new design not based on any previous games she was in. When Sakurai mentioned that suited Samus was mostly based on her Other M design (
right here in this video) I assumed Zero Suit Samus would also be mostly based off her Other M design. (I was 100% positive ZSS was returning.) This assumption disappointed me because I did not like her character model in that game. ( Other M < Brawl ) But now that we've seen her design for the upcoming game, it's much better than both Other M and Brawl IMO.
My point about Ridley is that if he is playable, he might be given the same treatment. His character design might not be anything like what's in Other M, Super Metroid or any other Metroid game. Other M Ridley would be ugly as hell when contrasted with other characters in such a bright and colorful game as Smash. Super Metroid Ridley, while being the most preferred design among supporters it seems (and I would concur if he was strictly based on an original design), seems to be kind of lanky. So I'd be willing to bet that Ridley will get a makeover. If confirmed to be playable (which I very much believe there is a significant chance of), it will be interesting to see how he is designed.