The more I think about it, the more Klonoa really fits in Brawl. Here are the reasons based on his abilities and game play:
Pretty fast
Wide ranged abilities (thanks to Klonoa Heroes, his ring can become many different weapons, such as a saber, mace, parasol, etc.)
Double Jump capabilities
A taunt (In Lunatea's Viel, there is actually a taunt button. This "taunt" also activates automatically after a boss is defeated.)
Also, thanks to Namco x Capcom, it seems that he has a great finishing blow, the Thunder Hurricane, which could be used as a Final Smash.
Besides the whole Namco/Nintendo relationship, Klonoa seems to be a fit representatvie for Namco.
His victory music could be the one from Empire of Dreams when a Boss Vision was cleared.
(Here is one of my vids with the tune at the end:
http://youtube.com/watch?v=QDBhsZdoWAY)
And what about Popka as an assist trophy? He could give your character an extra "boost" and also shoot up other characters into the sky so you can use a finishing move to send them up even higher!