hmm i'd have to disagree with rainbow cruise being a worse stage against lucario than japes and frigate. I havent played a Lucarios at Frigate much at all, but have a lot of experience against them on RC and Japes.
Rainbow cruise you're basically playing keep-away, using the stage's layout, until you get in a position to approach from below lucario with uair, or for him to mess up, and until the stage reaches an position you're less likely to get gimped. It's hard for Lucario to Aura Sphere effectively on Rainbow cruise do to the horrible layout of the stage for him. And gimping you on the stage is difficult after the pendulum phase, whenit basically turns into a walkoff. Speaking of that section, starting on the pendulum phase and going on until right before it returns to the boat, you can kill Lucario at ridiculously low percents. He's more susceptible to vertical kills than horizontal, due to his floatiness, so going for an usmash/uthrow here can get you an early stock. But yeah, lucario's ability to camp/projectile spam on RC is for the most part destroyed. His aerial game is still a problem, but isnt as bad as, say, meta knight or wario. Or marth >.>
In my opinion, Rainbow Cruise would be the least dangerous of the three stages against lucario (but i wont go into reasons to why the other two are bad against him)