Speaking of Shantae, how likely do you think her inclusion is? She was noted to be a popular request alongside Dante, Lloyd and Dragonborn.
I feel like she's been discussed fairly often. The gist of it is that her titles don't have raw sales and mainstream recognition like some other indies have, but the series has been going on semi-consistently for quite a while and developed a solid cult fanbase, and the Half-Genie Hero Kickstarter dropped during the initial indie Kickstarter boom, was able to capitalize on that fanbase,
and dropped at the right time to channel some of that energy into the Smash ballot. This all leaves her with a decent level of support in the Smash fanbase, enough for Sakurai to take note and secure her a Mii Costume. Plus, WayForward's a pretty solid supporter of Nintendo systems, so if Sakurai ever felt the need for Shantae, the negotiations shouldn't be too difficult.
Also, tying into some other discussion of Smash's lack of people of color, I will note that Shantae's SWANA-coded and has more melanin than like 90% of the current roster combined. I don't think there's any one ethnicity she's planned to be; her games seem to be more of a generalized "Arabian Nights" sorta thing, though I believe someone's looked at the inspiration for her dances and the geography of Sequin Land and theorized she's Turkish (Though I'll have to dig up that theory for reference). But yeah, worth noting.
If nothing else, Shantae is in a prime position to join Shovel Knight as a guest Assist.
I've wanted to say I'm kinda averse to "(x) could be an assist" comments, less because I think it's an insult to the characters and more that, well... I don't think many of these characters would actually make good assists. I get the appeal of giving characters a shoutout even if they're not on the roster, but a lot of these assists boil down to "person shows up, runs around, and throws out a couple different attacks" and it only makes me think "Man, I wish I could play as that guy." Prime examples of those "sorry, not a fighter"-type assists are Zero, Black Knight, Alucard, and the aforementioned Shovel Knight. I don't want to single out your comment in particular, it's just part of a general feeling I've had