As much as I'd like for Max's crazy MK in Smash theory today to be true, there's just no way that's happening because 1. I seriously doubt an MK character is getting into Smash just because a new MK game is coming to Switch. 2. A Warner Bros. Rep seems incredibly unlikely to me, 3. going by the datamine, the second fighters pass character is already in the code and most likely the next to be announced. 4. While stranger things have happened, I also seriously doubt Reggie is coming to an MK event to announce this, it would be on their own terms. Mortal Kombat being an M Rated game wouldn't even be the problem, considering we already have Joker and Bayonetta in there, and there have been more toned down MK games where the characters could be based off of, it's everything else that makes it unlikely.
If it did happen though. It would be absolutely be Scorpion. He's the most popular and most iconic character in the entire franchise. He's the sole character on the Mortal Kombat X and 11 boxart for a reason. This is coming from a huge Sub-Zero fan, by the way.
You have good points. I would still laugh if Max ends up getting an MK character anyway. He and Simmons sorta wanted/predicted characters like Little Mac, Cloud, and Bayonetta, and ended up getting them. He also really wanted Strider (though if my memory serves correctly, he only likely brought it up as an alt costume idea for Greninja). Some counter-points to your argument, however:
1. While true, nothing states it can't happen anyway. I'd say that
if we do get an MK rep, it isn't necessarily due to MK11's release on the Switch.
2. I feel like Sora's in a similar position, being an alleged Disney character and whatnot. Even if we factor in those companies, we're talking about
game characters, not cartoon characters who happen to star in their own games. Gigantic corporations they may be, I doubt the answer would be a hard "NO" without negotiations being heard first.
3. While yes, that's certainly what it looks to be right now, we don't know #3, 4, or 5 yet. Just because Erdrick/Slime/Sora/Bravely/What-have-you is implied to be next in line doesn't mean an MK rep isn't in the Fighter's Pass for that reason alone. We just need to wait and see.
4. I can see NetherRealm show off their game at E3 with Ed Boon teasing toward something. Whether it's MK-level guest character shenanigans, or foreshadowing into a Smash trailer without referencing it in the Microsoft/Sony panel, fact is that MK content will be shown on some level some time post-launch. If, hypothetically-speaking, we get Scorpion or Sub-Zero, I can see the announcement take place in Nintendo's panel.
Either way, it's easy to imagine what route they'd go with either of the Ninjas. It could be 2 alts (modern and classic) with the recolors based on the classic Ninja "rainbow" (i.e. Scorpion, Sub-Zero, Reptile, and Ermac), or go the full spectrum (i.e. Scorpion, Sub-Zero, Reptile, Ermac, Rain, Smoke, Noob, and Tremor).