-Being the highest rank in Mystery Dungeon doesn't really mean anything. Like I said, look at Gardevoir, who had an important role in the story.
-Pachirisu, Roserade, Electivire, Groudon and Kyogre are also costumes. Notice the last three I listed, and what happened to them. Speaking of Roserade, there could be something special about it. It's the only Pokemon to have gotten a baby AND an evolution in one generation, ever.
-Ditto, Transform. Chansey, Softboiled. Pachirisu, Discharge. Smeargle, Sketch. Castform, Weather Ball. Miltank, Milk Drink. Kingler, Crabhammer. See where I'm going with this? There are a lot of other Pokemon with signature moves, and no one is making a case for them.
-Lucario's aura ability isn't really that special. If I recall correctly, an Espeon can predict an opponent's next move based on air currents. As for understanding human speech, I always thought that was a silly thing for the Pokedex to say, personally. When you've got Pokemon like Alakazam that go beyond the intelligence of a supercomputer....it really is quite strange. >_>
Oh, and just to let you know, I don't have anything against you or anything, if you feel like I do. o_o You're a good debater, and I just like adding things to spark a discussion. If Lucario does make it into Brawl, then congrats. I'm just not liking the rabid Lucario fans with their "LOL, another Pokemon crushed! Lucario's so going to be in!" attitude. =/