I got it.
Even so, we could be able to switch between 1vs1, 2vs2 or 3vs3. I think it'd be a nice addition.
True what Havok said, but I agree with you that it would be cool to choose. In fact, if we're going with 2D, I'd go as far as to suggest alternatives to Arcade mode.
Arcade:
-Loner (1 vs. 1 battles)
-Partner (2 vs. 2 Battles)
-Team (3 vs. 3)
-Adventure (Whatever you pick vs. Random(random battles, sometimes 1 vs. 1 sometimes 3 vs. 3))
And then
Versus would follow a similar thing to "Adventure" allowing you to pick either 3 or 2 or just one guy to fight against your opponent. To keep it balanced, obviously the fewer players you fight with would equate to less damage taken from attacks. For instance: If you have one character versus your friend's 3 characters, then you don't take damage when you block non-super attacks. And even super attacks would do like 40% less damage.
I think I should also speak of
Co-Op in this part of my message. I'd like to be able to play with a friend against the computer. But Co-Op would be seperate from Versus, as both characters would be on screen at once. Co op can go up to 3P vs 3P or you can do 3P vs. 3CPU. CPU Battles would play out like Arcade, just with all characters on screen at once. But the number of enemies that the CPU controls would corrolate with the number of human players, so if you only have 2P, then there will only be 2CPU. You see?
I'd want for there to also be a story mode. But things would be interesting as there are so many characters, so you'd have story based on series.
Story:
X-Men: Apocalypse is causing all times of chaos and you're trying to fight your way to the source of the problem. (So if you're a hero X-men, you'd fight only villain marvel characters and vice versa) A spacial rift happens and people think a mutant has caused it, but then it turns out that it's something else. (Obviously this would be why X-men characters are in the game)
Megaman: After being left on the moon at the end of Megaman: Legends 2, Roll and Tronn call a truce and try to get Megaman back down. Everyone gets sucked into a portal on the way back. (Explaining how Tronn Bonne, Roll, and Megaman are in the game )
Avengers/Ultimate: (Hulk, Thing, Torch, Invisible Woman, Mr. Fantastic, Captain America, Spider-Man, Luke Cage, Iron Man, War Machine, Wasp, Hawkeye, Atom/Ant Man would all appear but it would be mostly based off the Ultimate versions) Galactus comes to destroy Ultimate Earth, but when Reed deploys a bomb to stop him, it warps away various people on the planet.
Street Fighter: In an Alternate reality, Bison wins at the end of Street Fighter Alpha 3. But his Psycho-Crusher bomb thing doesn't end up destroying anything, it actually warps away everyone nearby. (And anyone who has played SFA3, knows that literally EVERY character was there lol)
Deadpool: He just volunteers to jump into a warp portal, citing that "Everyone else was doing it, I just wanted to fit in!"
Darkstalkers: Dimitri is searching for information on his past, to see if he can become even MORE powerful. He uncovers a secret amulet that ends up warping away various people from his world...
So you get the idea. The story would focus on the series, until the characters are warped away and start fighting in other worlds. At the end, Apocalypse, Galactus and Bison would be Final sub bosses with a new random character (Maybe Abyss from MvC2), as THE final boss.
It's not too deep, but more than what we got for MvC2. The only other thing is that I'd like for there to be "cut scenes" between battles and character unique dialogue exchange when the battle starts.
Last thing?
Dream Battle:
You pick the characters to fight and then watch the battle unfold, this is quite standard to fighting games now, but it wasn't in MvC2 so it's worth mentioning.
It'd be bad ass to see an updated Morrigan sprite vs. someone new like Deadpool.