I wonder though.
What if Sakurai makes an all-new design for Ridley for Smash Bros. (not Other M Ridley) that's playable, so as to get around the whole "canon size" thing? Perhaps that is very much wishful thinking, however, there was a time where Sakurai had a playable and non-playable version of character in the same game (see ROB in Brawl, where enemy versions of ROB were confirmed on the Dojo before the game's release).
And to a lesser extent there was arcade-sprite DK at 75M.
As I said before, if Sakurai does confirm Ridley as a stage hazard, and then a few weeks later show him off as a newcomer (if there was a time to show off a newcomer for Smash Bros. within the next several months, September would be the one to do it, considering its the only month where there are no major releases to tie-in a veteran confirmation).