The guy you're looking at here is the playable avatar character for the new Nintendo IP, Daemon X Machina.
PLOT SUMMARY
We do not know too much about the entire game of Daemon X Machina, but we do know the plot.Half of the moon has crashed into whatever planet the story takes place. To rebuild society, mankind has developed AI (stands for both artificial intelligence and Arms of Immortals) to help in the reconstruction. However, an unknown and new type of energy that the moon emits called Femto corrupts the AI. As a result, mankind now wages war on its own systems that have gone renegade. The Femto energy has also enhanced select humans that come into contact with the rare. These humans are labeled as Outers, and are hired as mercenaries to destroy the corrupted AI and return the destroyed world back to its preconstruction state.
To combat the AI, mechas called Arsenals are constructed and piloted by the Outers to do battle. The Arsenals are completely customizable and can adapt by using the enemy's own weapons. They're capable of short-range, long-range, land, and air combat. ORBITAL, a neutral organization, maintains order within the small bubbles that keeps civilization as safe as they possibly can before the AI can attack. They're the home bases of these mercenaries and use their equipment to their advantage.
This is a bonus, but the soundtrack is a mix of synth and heavy metal. If that's your style, this game might have your type of OST.
WHY THE OUTER?
It's a fresh, new IP of both Nintendo and a genre that has yet to be in Smash Bros. The closest we've had yet is the possibility of Elma from Xenoblade Chronicles X, but the whole game doesn't revolve around mech action. Ad characters are, in my opinion, and inevitability.
WHY NOT THE OUTER?
Being a new IP doesn't suddenly equate into being a Smash Bros. character. The most notable example of this is with ARMS, a new IP that debuted on the Switch, but the highest it ever reached was at an Assist Trophy level. It may also be too new for this first DLC pack. However, we do not know when the origins of the game began, so it is not impossible, but definitely not within the first three characters.
In Daemon X Machina, you can attack and explore outside of your mecha, but the mecha is the entire point of the game. Unless the Outer is just using the default mecha that has been insanely shrunk down, shouldn't it be impossible for a moveset to be generated? Considering the Star Fox team uses a moveset that takes idea from the Arwing battles and takes it on land, it's debatable. The in-game mechanics allow the human form of the character to be modified, so an idea may be made to make a hybrid of using mecha weapons while being in human form.
MISC.
Here are some videos that give you a better idea of the upcoming game if you're still unfamiliar.