SlickSlicer
Smash Apprentice
I read somewhere that Sakurai said that there weren't many franchises from Nintendo he could draw from for Brawl. But as you pointed out with those latter two, there are plenty of Nintendo DS franchises that they could add characters from. My favorite being Phoenix Wright included (just for the lulz), Smash Bros. could totally also draw from the Megaman Battle Network games (or just from Megaman himself), Custom Robo Arena (a great game), Magical Starsign (Mokka appeared as a trophy at least ), Rocket Slime and moar. There's a vast plethora of untapped DS potential.There's also plenty of franchises that could still be represented like Animal Crossing, Custom Robo, Nintendo/Advance Wars, etc.