The list of datasheets is rather long, so here are some entries that would be particularly interesting or appropriate. I’m trying to lean international and lesser known here, but the Marvel Universe doesn’t make that easy. The list is still half New Yorkers.
Bishop: Mutant cop from a dystopian future. Maybe he got pulled backwards in time due to Kang’s shenanigans. He’s traditionally an X-Man rather than an Avenger, but his knowledge of the near future might convince him to stick around.
Beast: Mutant genius/civil rights activist. Who is also blue. Beast is a good fit for a prankster or scientist spot.
Black Panther: King of a technocratic African state. T’Challa would work as a finance guy, a technical advisor, or a straight up team leader.
Black Widow: Cynical russian super-spy. Basically just get a book of lewd Russian swears and use it liberally. She is, obviously, good at the espionage and sneaky side of things.
Clint Barton: Hawkeye. Either an ex-carney, ex-super villain trying to make good or a SHIELD agent. I have a preference for the misunderstood villain version, however.
Captain America: WW2 Super Soldier who spent the intervening decades in suspended animation. A pretty logical team leader, once he gets over the culture shock.
Doctor Strange: He’s an ex-Surgeon, so he’s one of the only comic book ’Doctor’s to come by the title legitimately. I’m not sure how Kang would capture a mystical heavy-weight like Strange, but he’d be a good magic advisor, obviously.
Hercules: The hard hitting, hard partying demigod. He’s a solid, cheerful heavy. Playing Herc will guarantee his Olympian relations mess with the team.
The Hulk: The harder hitting, mopier heavy. If you play him, the US Army is sure to distrust the Avengers.
Iron Man: Genius, billionaire, playboy, philanthropist.
Luke Cage: Hero for Hire. Just make sure someone is around to pay the bills and he makes a good heavy. Dude also would add more of a street level focus.
M: Another mutant, M is one of the few Muslim characters and has a list of super powers as long as your arm. She’d bring more of an international flavor to the team.
Monica Rambeau: Ex-cop who got super-powers stopping a super-villain. She was inspired by Pam Grier. She’s a solid blaster and a good leader.
Ms. Marvel: Ex-chief of security of NASA who got super-powers stopping a super-villain. She got fired from that job because she wasn’t stopping alien invasions with all 0 of the space ships NASA has. Basically Commander Shepard with a cape.
She-Hulk: Bruce Banner’s lawyer cousin who got a blood transfusion. Now she’s almost as strong as he is. She keeps her brains when she goes green, though. And her sense of humor.
Spider-Man: He does whatever a spider can.
Thor: Norse goldilocks. He comes part and parcel with Loki as a villain.
Wasp: Size-changing blaster / society debutante. She’s a friendly, social, supportive person. Also, crazy rich.
Since the team will grown and shrink, don’t worry too hard about this. But here are some bases you might want to make sure you have covered.
Financier: Someone should be able to pay for a home base and the like. Iron Man and the Wasp are traditional, but Black Panther, Thor, and Hercules would all be capable.
Heavy: Hit hard and get hit hard. Thor, either Hulk, Captain Marvel, Herc . . . lots of options here.
Genius: Someone capable of building the jets and gadgets the team uses. Tony Stark did it in the comics, but the Hulk, Beast, and Spider-Man certainly could chip in.
Leader: In game terms, this is mostly about making assets for other characters. Captain America is the usual choice, though Iron Man often tries and does a mediocre job at it. Monica Rambeau, Black Panther, or even Black Widow could do it.
Cheerleader: Not a great term for it. But the social, friendly person the holds the team together. Spider-Man, Beast, and the Wasp usually do it. Hercules and She-Hulk certainly could.
Blaster: Hitting things that are just out of reach is useful. Hawkeye, Iron Man, Monica Rambeau, and Ms. Marvel all fit the bill.