He's right. Did you guys play "Shonen Jump's Super Stars" for the DS? For one, it was in all Japanese. Two, SSB esque fashion. Three, it wasn't all that good (I only liked to pick Goku and Naruto). Finally four, there will be others to copy the exact same mechanics as SSB & still not be better than the orginal O.G. ya know what I'm sayin?
Orignal Original Gangsta?
Anyway, here's what I have to say about it.
Ridley indeed has much more potential than other Smash characters. While I won't discuss his moveset, I will discuss how he could fit. Basically, his main problem is not his size (seeing as Pikachu in comparision to Mewtwo is way too big), but his wings. His wings are twice as big as Ridley's total length. However, there can be a compromision for that. Basically his wings don't have to really look that big, it's mostly sideways anyway. Ridley has the ability to draw in his wings anyway.
So, often, when he's not in flight, the wings aren't visible. They are only visible when flying. Whenever he gets hit in the air, he pulls in the wings again. This saves a lot of visible space, which could block your sight.
There is a good chance he will be in, because of his popularity. However, since it's easier to implement both Dark Samus and the hunters, they would seem more likely. But there are some reasons why they wouldn't make the cut.
Dark Samus basically looks like a Samus clone. While I haven't seen it in-game, I do know that it's not. First of all every attack Dark Samus does is Phazon-based. Now I don't know if Dark Samus uses rockets, but if it does, they would be Phazon-rockets. Dark Samus also has somewhat the ability to fly, a thing Samus does not have. I also believe that Phazon creatures have additional tentacles, but I'm not sure.
Dark Samus can indeed be a very unique character, and it doesn't even need clone moves. However, because Dark Samus looks a lot like the original, only blueish, Nintendo might hesitate on adding it.
For the rest of the hunters I might discuss later.