Trimmed the fat a little bit since last time. 70 characters, 8 echoes.
Newcomers (Green): Inkling, Ridley, K. Rool, Ashley, Isaac, Badanna Dee, Geno. 7 in total with 5 yet to be unveiled.
New Echoes (Yellow): Daisy, Dixie Kong, Chrom, Isabelle, Dark Samus, Shadow. 6 in total with 5 yet to be unveiled.
I think this satisfies the "I hope you aren't expecting
too many new fighters" requirement while still putting fan favourites in the forefront of the base game.
I based the newcomers on mii outfits post-ballot and the general popularity of each character. Here on Smash Boards, specifically, K. Rool, Ashley, Isaac, Bandanna Dee, and Geno's threads have the most replies of non-deconfirmed characters in that order. I also took into account Japanese polling (as inaccurate as it may be). K. Rool is the fan favourite worldwide now that Ridley is finally in Smash. Isaac is not massively popular in Japan, being essentially the polar opposite of Bandanna Dee in that regard; their respective levels of popularity flipping in Japan and the West. Ashley is a breakout character that has been at the forefront of a lot of Nintendo's marketing the last couple years, most recently with her very large roles in both Badge Arcade and even more recently WarioWare Gold. Her Assist Trophy, something that caused a lot of people to be upset last time around, is also nowhere to be seen. Geno is the character with the most staying power of them all, being associated with Smash speculation in both Japan
and the West. This, coupled with Sakurai's own statements, the Mii costume, and Square-Enix's participation from the very beginning of production leads me to believe he will be in as well.
The Echo Fighters all seem like no-brainers. I don't believe Diddy Kong's jab being changed to remove his tail is a coincidence: Dixie Kong will be, in all likelihood, Diddy's Echo Fighter. Robin's Final Smash not being shown leads me to believe Chrom will be playable. If Nintendo loves one thing, it's FE:A and like it or not he's the most important character from Awakening that isn't playable. Why an Echo Fighter? Because Sakurai has joked that Chrom is basically a clone of Ike. I don't really agree with this at all, but in a world where we've been given an introduction on the concept of "Echo Fighters," it would be kind of bizarre to not include several. Chrom seems like a no-brainer for a safe Echo Fighter. Isabelle is like Ashley on steroids. Where Ashley has seen a huge explosion of popularity in Japan, Isabelle is probably the most famous Nintendo character introduced post-2010 on both sides of the world. Animal Crossing Pocket Camp is currently making Nintendo a metric crapload of money and throwing her in to advertise not only that but a future console Animal Crossing game is a really,
really safe bet. Dark Samus's Assist Trophy has not been seen, nor does Samus appear to have any Dark Samus alt costume. Dark Samus is another one of those characters that seems like a really safe bet for padding out the "Echo Fighters," and also throwing the West another bone in the form of more Metroid in Smash. Shadow is a really weird one. Obviously his Assist Trophy has been replaced with Knuckles, but the only reason I put him on here is a very strong suspicion that he'll be playable. I don't even especially want him to be, it's just a powerful intuition I have about these sorts of things.
I think this is probably the most realistic fanservice-heavy roster we could get. There would be very few people legitimately disappointed by this, and it lets the DLC venture into the realm of the more obscure.