Hmmm those are some very interesting picks and some good choices.
1) Sora from Kingdom Hearts, as the second Square representative. I do not believe Geno will be chose due to Square choosing characters that are current and that they can cross promote off of. I think Sora has a higher chance than a Dragon Quest character due to that he is more of a globally popular character. Compared to Dragon Quest whose majority of sales come from Japan, Kingdom Hearts receives most of its sales from more than one country. In dream drop distance the amount of copies sold between Japan and the USA was very close in number. This is why I think Square will choose Sora as aside from Cloud he is the next most globally popular character. As for stages I could see him coming with Destiny Islands and a remix version of the Destiny Islands theme.
2) Heihachi Mishima as the second Bandai Namco rep. It would be very odd for Bandai Namco to not have a second rep. Given that they are developing the game and will be the only 3rd party that does not have a second rep if Square gets another. It would make no sense that they would not tell Nintendo and Sakurai that they also want a second rep. The most logical choice I believe is Heihachi, we know Sakurai considered him when selecting the original Bandai Namco rep that eventually went to Pacman. At that time creating his moveset was too hard, but technology has improved and they have put characters with harder movesets in ex Bayonetta. Not to mention that he has already been in a similar fighter to Smash in Playstation All Stars. Also he is more relevant than LLoyd from Tales of Symphonia. As he has been in every Tekken game. For his stage I could see them choosing the Mishima Dojo. And for a song that he would come with I could see them choosing Abandoned Temple-Final Round.
3) Edelgard from Fire Emblem Three Houses. It makes too much sense especially since Nintendo is choosing the picks for DLC. The last time they did this they added Corrin for Smash Wii U. With Fire Emblem Three Houses being scheduled for release in 2019, it only makes sense for them to want to cross promote. As for why Edelgard, despite not being the main character she is the one that stands out the most from the characters we have seen so far. Im sure Nintnedo is aware fans of Smash are annoyed of so many Fire Emblem characters, so they may trying adding a character with a non sword weapon. Edelgard would be interesting enough to make fans want to play as her, as she would bring a different move set compared to all the other Fire Emblem characters. She could alternate between sword and axe based attacks, or just be an axe user. As for stage she would come with, given that the Church of Serios is an important factor in Three houses. I can see her stage being some kind of church like stage. And as for music unfortunately we do not know enough about the game to choose music. If I had to choose so far I would it would be the trailer theme for Three Houses.
4) A Pokemon 2019 rep. This game is also scheduled to be released around sometime in 2019. And being one of the later DLC's and potentially being released around the same time as the game. I could see them wanting to cross promote by adding one of the Pokemon to Smash. This slot could potentially also go to a Metroid Prime 4 rep, we will have to wait and see. I do not believe Katalina will be added, I think Nintendo will want at least two of the 5 DLC's to be some of their characters. If Katalina was added the majority of the Fighter Pass DLC's will be third party's and given that Nintendo is choosing the characters I can see them wanting to at least have two of the five being their characters.
5) Steve from Minecraft, as the first representative for Microsoft. This one makes too much sense, given the high partnership between Microsoft and Nintendo. And if you take into account Vergeben saying Minecraft was in Smash in some way then it is most likely Steve will be one of the final characters. Though I prefer Banjo, Steve is more relative and is one of Microsofts big IP's. It would seem more likely they would push for him as he could help them cross promote. Banjo hasn't had a game since 2008, and unless Microsoft and Nintendo are planning a new Banjo game together I don't them wanting to push Banjo, as iconic as he is. As for stages I could see him coming with a basic Minecraft builder stage, with maybe some creepers as stage hazards. Finding a song for Steve was really hard, all the songs are either too soft or some sort of parody's. If I had to choose one it would be Aria Math, but it would seriously have to be remixed to give it more of an upbeat.
Destiny Islands theme
Abandoned Temple final Round
Fire Emblem Three Houses Trailer Theme
Minecraft Aria Math