All I can guess is that Brawl didn't have enough characters in it for someone. I mean, Waluigi is cool and all, but I'd imagine that no one truly misses him for not being in the game. That said, he looks pretty awesome in this video. He looks like a badass because he is a badass.
The video even gives you some detailed closeups of Luigi's evil counterpart, purple clothes and miscolored nose and all. Of course, he's rocking his Mario Tennis racket, though he doesn't seem to use it as a weapon much. I'm not complaining, as I'm no hacker.
Seriously, these hackers are amazing. It's not to the point where we're saying that Brawl is the new Mugen. Yet.