I still say to just cut the Banjo Kazooie characters entirely, considering they literally can't get in, as they're owned by Microsoft. It's not a 5% chance, it's a 0%.
That being said, that amount of third parties in the list is too da...okay, I'll stop myself before finishing the reference. Seriously, though, it's too high. I'd say drop Bomber Man, the additional Sonic characters, Leon Kennedy, Rayman, Crono, Viewtful Joe, Earthworm Jim, and Geno entirely, leaving only Mega Man.
Here's why. During Brawl's development, Sakurai stated that he doesn't want a ton of third parties. This'll probably still hold true. The bar is also set quite high. Sonic the Hedgehog, the undisputed most-wanted character for Brawl, barely got in on time, despite requests. Mega Man isn't even Sonic-level, but he comes the closest...by far. The support for others is practically non-existent. Honestly, the only non-Mega Man third party character that should really be on there is, as Neon said, a Namco rep. They may lack requests, but Namco-Bandai is helping to make the game, so they at least have a reason.
Even still, barring third parties, the list lacks the more popular characters and instead includes some unpopular, and frankly bad, choices.
Some that stand out like a sore thumb are King Boo, E. Gadd, additional Trainers, Paula and Rosalina. With King Boo, E. Gadd, and Rosalina, there is already too much competition within the Mario series between the likes of the more popular choices (Toad, Waluigi, Bowser Jr., and Paper Mario). These choices come up close to never. Paula is from a series that gets little requests to begin with. Even then, she is outshone by Masked Man, Porky, and Kumatora in Japan. The Pokemon slot is a different can of worms, with people with their own opinions on Mewtwo, Lucario, Zoroark, Genesect, etc. These guys don't seem to have the popularity to get in under these conditions.
As said before, even then, the choices of Waluigi, Krystal, Masked Link, and Ghirahim are questionable at best, but still better than the former five.
Over all, try doing some replacements...