I just got done playing xxPatgxx for a good long while and I'd say that this match-up is 55-45 in Olimar's favor.
Just to knock this whole stage discussion in the right direction, I'm going to agree with the person before me who said that counterpicking is more about emphasising your strengths in the match-up while closing off opportunity to strike your weakness, not where Olimar is worst at.
With that being said, I'm going to say that Lucario would probably do best on Orpheon Frigate. The reason why I say this is because the key to Lucario winning is actually being aggressive on Olimar. On the first part of frigate, you have that platform to camp under. Even though it's not the greatest, it does off your some cover from Olimar's Side B and a possible landing zone for recovery should Olimar choose to instant ledgehog you with his tether (he does NOT have to be offstage to do this and it is completely lagless). The other side of Frigate allows you to continually push Olimar offstage because it has no ledge for him to grab on to. The fact that it rises and falls is only going to make things worse for an Olimar trying to recover.
The second part of Frigates offers both of you platforms when trying to recover but neither of you should really be getting too much use out of them because of your knockback angles. The downward slope makes it harder for Olimar to land smash attacks and since Olimar will most likely camp from the center, you shouldn't have too much trouble exploiting that with your smash attacks or massive Aura Spheres.
As far as the match-up goes, Lucario cannot try to outcamp Olimar because it will never work. Olimar's Side B not only consumes your attack but it comes out a lot quicker and can be used in a manner that allows Olimar to hop over your Aura Spheres while still hitting Lucario. What you'll want to do is get a fully charged Aura Sphere to pressure Olimar so that you have an easier time getting him to change his position.
From approaching, I would reccomend Lucario using his Forward Air shorthopped because he should be able to retreat or launch an Aura Sphere if Olimar is trying to Pivot Grab or Forward Smash him in return. Be aware that if you get near Olimar, your roll is incredibly fast and can allow you to escape his attack before grabbing him and tossing him off the stage. Try not to get predictable with this approach. Remember that Lucario also has a good N-Air to knock off incoming pikmin as well as push any of Olimar's aerials out of the way.
For Olimar it's easiest for him to rack up damaging by using his Side B. Any other damage usually comes from punishing or early grabs in the grab. It is very difficult for Olimar to approach Lucario and even more difficult for him to punish one that stays in the air, but when he does its going to hurt. The main reason this match-up is in Olimar's favor is because of how quickly he can rack up damage and kill Lucario without putting himself at too much risk using long-ranged and powerful Smash Attacks. Its also very difficult for Lucario to KO Olimar.
I helped.