The first 13

The premier should have more characters than the original game had, but not too many. I think Mario, Link, Kirby, and Pikachu all need to be in the first 4 showed. Similar to Brawl, they start fighting

Samus should quickly appear of course with her bombs and lasers.

Fox would also appear using his blaster.

Ridley would come from the sky. He starts to attack everyone except Samus.

Starfy comes to the aid of Kirby and shows a fighting stance against Ridley. Ridley taunts and Starfy unleashes a final smash on him.

Geno should start by coming to Mario's aid. Showing off a few of his moves as well.

Little Mac should appear next to Link's help. He'd show a variety of punches on Pikachu.

Lastly, Mewtwo should appear to aid Pikachu. He'd enter by shooting down Little Mac with his shadow balls.

Megaman should be last for the surprise of course. This would really top off the trailer.

Geno

First AppearanceSuper Mario RPG: Legend of the Seven Stars
1995
Super Nintendo

The most popular character from the cult game, Super Mario RPG. For some reason, everyone loves him. There's only one problem: Nintendo doesn't have the rights to him. Technically Nintendo owns some of the rights to Geno, but Square Enix has some of the rights still.

Possible Moves

Geno would need some imagination, but he could still have several moves based off of his moves in Super Mario RPG. Maybe his boost could make him more powerful defensively and faster for a brief time, but would require him to take a couple of seconds use it.

His Geno Blast could be another move. It could hit multiple enemies, just like in Super Mario RPG.

The Geno Whirl is another possibility. He could shoot a ball of light at an enemy. It could be a charge-up move and do a LOT of damage, but not knock the character (similar to Fox's blaster)

His standard special attack is obvious for me, his Geno Beam.

And for his final smash, I think his Geno Flash is a perfect fit. It could light up the stage and shock everyone, basically a more powerful Zapdos.

An obvious choice, but in order for Geno to appear, Square Enix needs to just let Nintendo use the rights. They haven't used Geno in over 15 years, so why hold on to him when they could get free publicity for him and get him popular enough to actually star in a future game.