I doubt we're getting his Klassic edition. He's memorable for both versions. Right now Ed Boom is pushing his modern era design, which is far more different. The Klassic version is purely a costume last I checked. MK11 is also coming to the Switch, so it's likely the Klassic version will stay a costume.
Show me a third party character that doesn't look similar to their initial design.
... Sonic? At best. Meaning... he isnt short and chubby but is mostly the same.
I think when the general populous thinks of Mortal Kombat, they think of their original designs, which have been pretty much a focal point until recently (three games). Even still, Scorpion and Sub Zero have the same skeleton.
It doesn't matter what Ed Boon pushes- he just wants the character used.
It doesn't really matter that MK made palette swaps notable. That's not really a key factor in representing MK. Not compared to things like its unique combo system(which is kind of akin to Marth's Dancing Blade when it comes to directional inputs), the blood/gore, and extreme violence and finishing moves. Many of those swaps only became characters due to being glitches as well(which is what got us Ermac alone). The game evolved from that as well. It's one small piece of its history that is easily represented by having Scorpion or Sub-Zero's costumes be different colors not unlike those ninjas. That represents it where it matters in Smash, as costumes. You can even have their modern and klassic designs, 2 of each. Probably just sticking with Scorpion(Modern and Klassic), Sub-Zero(Masked Modern, Klassic Unmasked), Reptile(Modern and Klassic), and Ermac(Modern and Klassic). It also covers the four main colors in Smash, Yellow, Blue, Green, Red.
Again, just all opinion, and I argue, not based on much. The history of the character is what Smash Ultimate is about celebrating. De facto, the palette swaps were a core component of the original games, which is why they had as many characters as they did. Whether or not you personally think this is important is irrelevant.
You also missed a key component of what makes MK what it is- which is its campiness. Notice how the thread is even called "Toasty," which is a reference to a camp aspect of the game.
One more point- its odd to me that your entire argument in any of these points against Sub Zero, is that Scorpion would be based on the modern version (and seemingly, solely based on him). Yet- you ignore the fact that MK11 has different Ninja's included than the ones you list, such as the black ninja, Noob.
If we are doing an Echo(which isn't too likely as their bodyshapes are a bit more distinct now), then it shouldn't be for some silly reason like the palette swap joke. That only applies well to Ken since he was actually a direct clone. None of the MK characters were clones in this case. There were some, like Smoke, the glitched version of Ermac(before he became a character), and unmasked Sub-Zero. As well as conceptual ones that replaced some earlier characters, like Shinnok for Shang Tsung. Mortal Kombat 4 did that more than once. Tanya was a stand-in for Kitana, but also had similarities to Mileena. Scorpion and Sub-Zero were never actual gameplay clones either. That's why the comparison doesn't work. The actual similar moves was something the entire cast had, with the two aerial kicks, the leg sweep, and the uppercut, and by default, every stage fatality used an Uppercut. Some of these stayed the same, but most of these were changed up to further make the gameplay distinct. Clones still exist, but it doesn't apply to Scorpion or Sub-Zero(who were never actual clones of each other to begin with). The only other similarity they had were using the same weapon in combos, which showed they reused a few assets, but they didn't based them off of another in the same way as some games do. They aren't comparable to the shotoclones at all. It's apples to oranges.
You just don't think of echoes the way I think of them. And I would argue, you don't think of clones correctly, as you seem to argue reasons only stated by yourself. What do Roy and Chrom have to do with each other, exactly? Chrom should play like Lucina and Marth, by his game standards. He isn't even in the same timeline as Roy as far as I'm aware. And what difference does this make?