I tend to rely on whatever evidence I could muster to prove a character's playability, and I do see a ton of credibility in the trophy quiz rumor. Why I insist that the Zelda newcomer would hail from Skyward Sword (or in Impa's case, be modeled after her appearance in said game) is due to Fi's trophy, and the music that plays--which in turn hints towards either Ghirahim or Impa. Other major characters that could technically sneak in include Demise and Groose; the former, however, is an easy alt for Ganondorf, while Groose...eh...not very likely. I leave my options open, and once I heard confirmation that other characters could potentially be alternate skins, I ultimately concluded that Ghirahim is more likely, but is by no means a guarantee (if Chrom was anything to go by).
The flaw I have with the whole "representing the franchise," as much as I agree with that sentiment, is that in Zelda's case--as well as Mario's case, even prior to Rosalina's inclusion--is that the entire franchise in general is already represented; all that was truly needed was the Triforce Trio, and one representative from the Toon versions of the game--specifically, Toon Link. I get the Toon Zelda/Tetra requests--I really do--but the Forbidden 7 aspects of Brawl doesn't necessarily give the characters listed there any extra leg. After all, Roy and Mewtwo were the only characters in that list that almost made it on their own accord. Similar to Plusle & Minum, it is likely that Toon Zelda/Tetra, as well as Dixie Kong and Dr. Mario, were all heavily considered, but never even worked on for the final game.
I typed something up with 8-Bit Mario in regards to an incomplete moveset, but let's just say, he'd be dependent on a moveset around what he could do in the Arcade Donkey Kong games, Mario Bros., and Super Mario Bros. in particular, with perhaps a few bones thrown into other original Nintendo games from their Pong console to Tetris. His colors would be red, white, green, and blue (for Jumpman). His Final Smash would have him turn into the Duck Hunt Dog, and you shoot the ducks in order to spike your foes; it would be a combination of killing your opponents and keeping the FS going for an entire "level" of Duck Hunt. Try to use your imagination; you might come up with some pretty cool ideas, yourself.
I used to have my doubts concerning Dark Pit, until Lucina happened, and then I begun to take into consideration the very real possibility that this roster could very well be huge. I'm not giving him the guarantee yet (like I have with Ridley and Shulk), but considering that he's been teased, he's very likely. Although I'd much rather see Hades as a third representative from KI:U.