Captain America (team leader. I do not however have any problems with Iron Man being the leader in the A:EMH-cartoon nor the possibility of Cap not being the leader in the movies. But I have been a loyal follower of Steve Rogers ever since I read the Secret Wars-books where even the Thunder God said he would follow him above any of the others present)
Ant-Man/Giant-Man (Henry Pym, the adaptation of him in A:EMH I think is almost perfect. Also it's important to have a scientist on board)
Invisible Woman (I think she was a member back at the end of the 80s. She is by far the most powerful member of the Fantastic Four in my opinion. I also think she has a really strong character)
Spider-Woman (Julia Carpenter) (I have not read much on her but I think she has grand potential. I think Spider-Man is better a solo hero, occasionally teaming up with others. And Jessica Drew I'm actually slightly tired off, she's was overused by Bendis)
Quicksilver (A character I think is underappreciated and underestimated. He powerful and incredible useful. Also he has that exciting "former villain"-aspect)
Vision (a classic character, I love him. Still unsure on my feelings towards Avengers Disassembled)
I think these six are a strong bunch, and even more exciting personality-wise but four reserve members are needed.
Captain Britain (for the times they are fighting mystic/magic-users. It was either him or Doctor Strange. I also think and Captain America together is quite exciting. But of course he can't join the Avengers if England is ever threatened by the same time which is quite usual in comic universe)
Thor (for those truly powerful foes, it was either him or Hercules. Though he could be the one most boring personalty-wise and does not really have that strong relations to anyone else on the team except Cap and Pym. Maybe I could have the Eric Masterson-version instead for the sake of variation)
Beast (no constest as to which mutant-character I should have. I'm tired of Wolverine, which is sad because he is a great character. Beast and Ant-Man together are also a brilliant pair of scientist)
Sandman (villains-turned-good is something I really like. I wish Sandman had been an Avengers longer. He is also insanely powerful)
As I'm thinking it through I could possible switch out Thor with someone a bit more original like Justice or Gilgamesh (!!) especially since both Quicksilver and Invisible Woman (and even more so with additional power of Sandman and Captain Britain) are quite powerful already...but meh..
After thinking more about it, I would really liked to have included Stingray as a reserve member even though he's only been a member of the Secret Avengers as far as I know. The reasons for this is the addition of another scientist with an entirely different field as well as a character with a battlesuit instead of powers.