The easy answer to the size debate is "Look at Olimar, he's actually the size of a quarter" and that's totally valid but Ridley is still an enormous dragon.
How is that different=??? Just change the size but keep the same body composition, or alter the body composition a bit like Charizard, who also happens to be "an enormous dragon" (albeit a heck of a lot less interesting in every single way IMO).
Thus, it's not even an argument, and it never was.
Do you want my honest opinion as to why we haven't seen Ridley as a stage hazard yet? Honestly? Sakurai does not want to disappoint the fans. He knows that lots of people want Ridley. He knows that if he flat out announces that Ridley is a stage hazard, people will be upset. By teasing Ridley fans with the shadow and the trophy fake-out in the Smash Direct, he's giving you hope. Alas, there is no hope. Other M Ridley is a stage hazard. Done. 100%. No question.
Yes, but making your fans wait to disappoint them is a terrible long-term proposition. It's also not something Sakurai has done.
See: Ness in Brawl. He was outright "deconfirmed", and yet, afterwards, he got hints. First, Onett. Then, Lucas being different from Ness with all of his non-special attacks. Then, Lucas not being at any of the demos when all the other pre-release revealed newcomers were.
That's not to say Ridley can't be a boss or playable character or a DLC playable character, but just doing that by keeping their hype consistent on purpose and openly just to disappoint them in the end is bad. That's how you lose money and lose customer faith.
It's bad business, which, after Brawl got such negative and dividing reception (including kinda by Nintendo, hence it not being at MLG and why all of the Smash Invitational players being Melee fans and a lot of them not playing Brawl), that's not good. It also doesn't help when the WiiU is not selling that well.
It also doesn't help with Ridley probably conceptually is such a great idea. The only problem with him is that Ridley conceptually blows Charizard out of the water, which may be why Charizard is still the dark (lol Rock Smash is the dumbest attack, along with his poverty Shadow Claw). Literally it exposes Charizard for one of the worst designed characters in Smash history.
Ridley was never teased (like that) pre-Brawl. In fact, he sorta de facto deconfirmed him via mentioning Norfair as Ridley's home turf and revealing Ridley's theme remix in Brawl. Heck, the only time Ridley was kind of teased was in the Melee opening, but that was more just a showcase of the various character's history.
Still, I do agree here: I do think Other M Ridley is a stage hazard. However, I think knowing that classic Ridley has a better body composition for Smash (in terms of being unique; Charizard is very similar in build to Other M Ridley), and quite frankly was more wanted.
Thus, I conclude that Classic Ridley will almost definitely be playable.
This switcheroo would be similar to R.O.B. being a common enemy then a secret playable character at the same time.
Really, if you want a deconfirmation to settle down a fanbase, you do it the way that all the Assist Trophy characters were treated: do it directly.