Ok, I'm making this list from a fan/marketing point of view. This is Hasbro now. So I truly believe that they will also take what was done in the past, and try to "up" it. That's just smart marketing. But, I know that from the M.U line, they really dig throwing out some obscure characters for us.
Series 1:
-Ultimate Hawkeye
-Bucky Cap
- Mockingbird
-Iron Patriot
- The Hood
- Daken
- Madam Hydra
- Sin (?)
BAF: Terrax
Series 2:
-
Commander Steve Rogers (Pump up that Avengers marketing)
- Future Foundation Spider-Man (Come one, it will happen)
- Red She-Hulk
- Iron Man (Bleeding Edge Armor)
- New Venom
- Rictor!!!!!!

- Marvel Boy
- Ares!!
BAF: Onslaught Reborn ( Yeah, I went there. SO WHAT!)
Two-Packs
- Mettle and Hazmat (Avengers Academy)
- Stryker and Veil (Avengers Academy)
- Luke Cage and Iron Fist (both Modern)
- Deadpool and .... some member from Deapool Corps