We might not get a first party among the fighter's pass. We might get one. That's about as much real information we have on the DLC design. The only reason to believe it's all 3rd party is because a 1st party is "expected", but the issue is there's tons of them, and no way to know how they're going about it enough. Are spirits actual disconfirmation, for example, would give us something to work with.
Other things to keep in mind is how Sakurai intends to implement a character. If he has an idea for someone, he may never change his mind(Dixie is one notable example of this, as her being a tag team may be the only reason he hasn't put her in the game yet, unable to make that mechanic work) either. Now, of course, making her an Echo or semi-clone might be a cool route too, but that only gets her in, not makes her fun or unique by design inherently.
Adding characters is cool. How you actually make them work is really important too. But to be fair, when it comes to speculation, not everybody cares about how the moveset is implemented(and that's fine, it's not like it's their job to come up with a moveset. They aren't making the game, after all).
