At this point, I see the following as being up to personal preference:
-DK Newcomer
-Pokemon Newcomer
-Zelda Newcomer (Less essential than the rest)
-FE Newcomer
-3rd Parties
-A couple of new series (in my case, Xenoblade and Murasame)
Other than the very strong candidates (Palutena, Mewtwo, Takamaru), the above are to me the most probable Newcomers we'll be getting. Hence why we're seeing a lot of minor differences shared across personal rosters, based on preferences and/or perceived merits (Robin over Chrom, Vaati over Ghirahim, this over that, etc.).
As a side note, I find a Zelda Newcomer to be much less probable than the rest, as we already have the central cast, and have the main and toon continuities. If we are to get a new Zelda fighter, I think it would most likely be Tetra, since she would be the second fighter from the Toon continuity; I chose Ghirahim because of preference.
And I did note Vaati's merits in my post in the Display thread. If I had to make a guess, I'd place priorities at Tetra>Ghirahim>Vaati>Tingle>>>>>>>>>Wolf Link/Midna.
What I did in the construction of my roster was to consider the essential characters. Basically, this equates to Main characters, Secondary cast, and Rivals/Villains.
Metroid, DK, FE, KI; these are among the franchises that lack essential characters (e.g. Ridley, K Rool, recent FE character, Palutena). If Smash is about including All-Stars, then there are still missing characters in many Smash series.
For Star Fox, we have Fox (the main star), Falco (prominent secondary character), and Wolf (main rival). I've only played SF64, so perhaps this affected what I perceived as essential SF characters.
I can certainly see the merit of adding Krystal to the cast, given that she's a prominent secondary character in the SF series post-64. The reason I didn't add her was because I perceived other characters to have more urgency than others when it came to inclusion. And since I didn't want to overstuff the roster, no new SF character was added.
Otherwise, I would have totally added more characters, like Krystal, Isaac (Golden Sun), Lip (Panel de Pon), a new F-Zero character (Goroh/Shadow), etc. I think I'll go to my original post in the Display thread and make an amendment as to why these characters didn't make my cut. Thanks for getting me thinking, Joe.