I'm gonna touch on a couple options for the "promo" choice that I thought about. Inkling was an obvious one, but honestly I think they work too well as the segue into Ultimate that I would feel wrong detaching them from that identity.
So then it came down to Azura from Fire Emblem Fates, and Yuri from Fatal Frame. I think both of these characters have a lot of compelling things about them. I'm wary of building up Fire Emblem too much, knowing I'll probably be dishing it at least one new character next game as well. But Azura is a lot of things - she's a singer, a dancer, a water elemental, and a lance user. Corrin was sold to Sakurai on their moveset potential, and I think Azura could fare similarly in this outcome. Yuri has less obvious moveset potential, but she comes from a fairly long running series that Nintendo now has direct stake in. While this is kinda sorta not a Nintendo character, I'd say she counts here (after all, she appears in Ultimate as well). It's enticing to introduce a new series to the game, one that fulfills a somewhat similar role to Bayonetta in the real Smash 4. And the Camera Obscura, as well as potential spirit summons may offer more abstract potential, but it would be really satisfying and unique to see it come together.
I really wanted to pick Yuri here, but upon more reflection I feel like if I'm not able to use Bayonetta for this role, I probably shouldn't use her either. A bit disappointing, and I already know I'm gonna end up with more Fire Emblem characters than I wanted, but I actually really like Azura's potential and if nothing else I've become more keen on the idea of a Fatal Frame character in Smash too. So it's a win win, now I want two characters I didn't really care about before.
The rest is really simple. Ryu is Ryu. I didn't go with Cloud because he was in Brawl, so instead we're introducing Konami's first character in Simon. I prefer Simon to Snake for this purpose because my preference does skew slightly toward those more intertwined with Nintendo history when possible. This frees up a space for Ultimate too, so stay tuned on which third party I'll use there. I'm just getting Charizard over with here too, because he was starting to feel overdue and I'd rather not waste any space in Ultimate on two Pokemon (Gen 7 needs to get something). I assume that both Simon and Charizard would have been popular ballot choices as well, so there you go. Azura and Charizard wrap up back around with the fire vs water theming too, kinda cute.
Sceptile, Archeops, 
(Garchomp)(Golurk)(Braixen)
