But it is easier to avoid small boss...anyway, there is no point in resizing Ridley if he is a boss, especially on a large stage. Its like if you would fight Ridley with size of Charizard on Pyrosphere in Brawl if it would be here.
Kinda like that, but with a little bit bigger Ridley:
Everyone else can just run away from him and he will most likely not reach them or will attack only 1 or, if he is lucky, 2 of them while everyone else laughs at him and those who failed to escape. I know a bit about Dark Pit (he can fly, unlike Pit, for example), but i doubt he has something that would really help him on such stage, unless he shoots fast homing smart bombs.