Putting these two together.
But even then, I don't see a trailer cutscene included.
He may be popular, but he's not a veteran.
If we get one, it'll be just a normal trailer. Like Sonic's.
I just don't see a point to make him just as special as any newcomer.
He isn't as special as a Newcomer. On this, I think we can agree.
He isn't as ordinary as any other Veteran, either. He may not get anything. But he has enough going for him, even if only a little, to get a Sonic-esque gameplay trailer that lasts 40 seconds or whatever.
I would argue this to be the minimum of what we could expect (and the minimum of what he'd deserve). Anything more may be asking too much, but it wouldn't be unwelcome, and could well be warranted anyway given his massive popularity. Which segues to the next point below.
What? Popularity?
Cause that's all I see. Call me stubborn.
But him being cut doesn't mean much IMO.
Sure, it'd be big, but would it be big enough?
Yes, popularity. That is precisely it. That, and nothing else (barring his Pseudo-Veteran status).
It's the only thing going for Mewtwo. But when you consider his immense global popularity -- which, apparently, beats out even some of the most popular/requested Newcomers -- then the matter may be worth looking into.
A reasonable move, therefore, would be to give Mewtwo a little something -- again, a minimum of a small Sonic-esque trailer would be sufficient to generate the kind of attention that would benefit the game. If you have a hugely requested character, revealing him with just a little bit of fanfare will increase overall game interest more so than if he were simply announced on the POTD updates (since video trailers and Directs innately reach a broader audience than Miiverse pics).
And I think that's the problem.
Since he's not in Brawl, apparently that makes him some kind of legend.
A miracle, if you will.
Apparently we need everything for this guy. The red carpet, the limo, everything!
Or, maybe it isn't really that big like everyone wants it to be.
He's legendary because of his S-tier popularity and demand in this post-Brawl cycle.
And because he's a Legendary Pokemon.
Mewtwo being absent from Brawl is notable only due to how it means he hasn't been in a Smash game since his last (and sole) appearance 13 years ago. That's a fairly notable span of time, and most likely has contributed to his present levels of popularity and demand -- that, and perhaps in how his cut was viewed as unjustified by some.
As a result of these variables, it is not unreasonable to get the bare minimum homecoming package (~30-40-sec gameplay trailer), and perhaps even more (perhaps not on the level of Newcomer, unless Sakurai and Friends decide to label him as such).
To reduce this whole topic to its simplest form:
-Tons of people want him in, or have expressed interest in him in the post-Brawl era
-He's been gone for over a decade in Smash series chronology (2001-2014)
-Ergo, promoting his return would be a smart marketing move, since hype=money
-The scale of this promotion should correlate to the amount of interest in the character; the greater the demand, the more attention Mewtwo's return should be given
The last point is where things are left to Sakurai's discretion, since only he and his team would know how high Mewtwo's demand really is (as it is their business to find out).
All of this to say is that if Mewtwo deserves special treatment, it's because his situation and status warrant such treatment.