Let me put it this way, the only way there would be no cuts is if this was a direct port.
I mentioned this somewhere before, but given what I've seen if people want all veterans back including lets say 10-15 new characters, I'm looking at a roster of around 70-75 or so (From Smash 4's 58). That's already a massive roster in of itself, and I'm assuming people also want DLC on top of it.
That's simply not true. You can make a completely brand new game by using stuff that's already been developed for previous game. It happens all the time.
Hell, take Mario Tennis Aces for example. That game is 100% brand new and it reuses all of the character models from Ultra Smash and then updates a few like Mario, Luigi, Wario, and Waluigi.
Your claim that the only way all the veterans can return is if this just a direct port is based on nothing. It's an unsupported claim.
Now that doesn't mean we can never have zero cuts. But even with a two or three year dev period a 60 veteran roster is still massive. And would probably give us maybe five newcomers at best. If we even get everyone back.
So again, it leads to what is more important. Do we want veterans or newcomers more?
This is all just assumptions based on nothing. Why on earth would they remake every character from scratch after they literally just got done supporting the last game.
We're not jumping from Wii to an HD console so what is the point of making all the characters from scratch. How many characters have changed over the last two-four years?
With all these Wii U games being passed off as Switch games, you think they would have to make everything from scratch and also somehow manage to do it in TWO years?! I mean they could. But, why? They just got done making perfectly good character assetts that could easily be passed off as Nintendo Switch models AND they are characters people love, want, and EXPECT to return.
Why wouldn't they just use what they already made as a basis to create a new game? Not to mention with all these Deluxe/Definitive Edition games, even though Super Smash Bros for Nintendo Switch is a sequel, people are going to be expecting the characters to return from the Wii U & 3DS version. Especially when the last characters added to the game were 2016. That wasn't very long ago.
And the 3DS is still being supported. People are still buying and playing Super Smash Bros for 3DS. Why alienate consumers and fans by cutting characters from the 3DS version?
People will be torn between going for the version of the game that has the characters they like better and possibly passing up the Switch version for the 3DS version. That's the whole reason Smash for Wii U & 3DS don't have exclusive characters to begin with.
But, I digress. The point wasn't that you said they wouldn't do this, but that you said they CAN'T do this. So why not? Why CAN'T they reuse assets from the previous game like SO MANY games already do?