Damn you really hate Jonesy that much huh? I have to go with whatever has Crash. I seriously don't care who gets into the game after him. Fortnite really doesn't bother me, but personally I think it's much too soon for them to make it into the gaming hall of fame that is Smash.
I wouldn't say it's basically impossible. We can form a really reasonable idea of what they'll do based on precedent. Of course, we won't get it right every time, but we can pretty easily determine what the reasoning behind adding past characters was.
With first party DLC, Nintendo leans HEAVILY towards promoting recent games. With 3rd party in general Nintendo almost exclusively has added characters from franchises with very high sale numbers and/or that are well established/classic. Literally the only exception to this has been Bayonetta, and she's practically a Nintendo character.
Regardless, I do hope you get one of your most wanted characters. Gengar in particular is one of my favorite Pokemon of all time, and I'd love to see them get in. When I was a kid my imaginary team I made for myself was Raichu, Ditto, Marowak, Alakazam, Gengar, and Dragonite.
Yea, it's hard for me to ignore the Mii costume and how scummy it would be to release Tails after that. I probably wouldn't complain for too long because I prefer Tails over Eggman, but I still feel like they would avoid that just because of how it looks. I hope I'm wrong because Tails is such an endearing and awesome character to me. I've been playing Sonic games since they came out on the Genesis.