Olimar... is an interesting beast.
well, let's look at several aspects of him and lucas fighting eh?
Olimar's abilities to fight change depending on the pikmin he has in stock. that's the most basic rule of the little guy. If an olimar has a red or yellow pikmin next in line, expect him to try and spike, if the olimar has a purple, except any smash, aerial, or attack for that matter, if a white one is next, except a grab or a throw. if it's blue, a grab or a throw.
Of course, that's assuming the olimar is perfect, which they rarely are. Another thing to watch out for is the pikmin that's last in line, as that becomes the pikmin that is at the end of the up special, a significant attack on the ground, as a purple pikmin can end it quickly.
This matchup depends on many things, but most of all, in my opinion, how good the olimar keeps track of his pikmin, and how well you do so too. There are many things that can curve this match in favor of the lucas though. the bulk of lucas' attack uses electricity, meaning, that after a good amount of fighting, it's not unlikely the bulk of the remaining pikmin will be yellow. If you use PK fire, you can change this. Yellow has spiking properties , and is good for the lucas for onstage combat, as you cant scar downward through the stage.... can you? Red has generally good knockback overall. out of the two, I'd prefer to have yellow pikmin to fight.
quick, strong attacks are the name of the game aganst olimar. dont decay your forward smash, and the olimar can die as early as 60-80 from the center of the stage, even if the smash isnt charged.
his small size makes him an annoyance to fight in the air against. SH DA seems very effective, and SH NA seems far too difficult to use on olimar to bother with. shield pressure tactics work nicely against olicar, and using forward tilt makes for a decent attack, though staying off the ground alot is recommended, as both the downsmash and forward smash of olimar cover him quite well.
Sorry for the ungodly long post, but these are my views on the little hocotate alien. This is one of the matchups that seems tu curve in favor of the olimar as the skill of the players increases, when the olimar and lucas are both scrubs, then it appears to be about even, however, as the two get better, the olimar should have the advantage, as all of olimar's skills can be fully taken advantage of.
As I said earlier, the name of the game is keeping an eye on the pikmin olimar has.