Speaking of 'leaks'
Awhile back Relaxalax brought up the idea of an "Assist Mode Assist" system due to Lyn appearing in Roy's trailer.
And now watching Roy's Smash4 trailer, the exact same thing happened there. I'm 100% positive it was just a reference.
Yeah, I wasn't aware of that when I first mentioned Relaxalax's suggestion (based on someone else's), but that seems to be more likely the case.
It did remind me, though, of an idea I had after seeing the August Direct--after seeing Alucard's assist trophy, it was interesting how involved his moves are. Would completely break the game if you could play as him, but I thought what if there were a separate mode where you could play as certain assist trophies (Lyn, Bomberman, Zero, Ashley, Alucard, Waluigi--not the moon, unfortunately) in a fun casual setting where balance doesn't matter to the same degree as in more traditional modes. While I'm not a dev and can't speak to how difficult that could be made into practice, it would seem like less resources than making an echo, and definitely less resources than making a playable character where they need to be balanced, and would be a nice compromise lessening the anxiety around assist trophies. Most certainly not happening, and even if it were I would have expected it in that Direct where they went over modes. But it's what I immediately thought of when seeing Alucard.