Yay! Another List Breakdown [http://www.escapistmagazine.com/forums/jump/6.842284.20720516]!
1) Diamondback: If they bring her in, hopefully there will be at least a partial-rewrite of the character. The "love at first sight" concept is probably something should be dropped in exchanged for a more general romantic tension between the two, culminating in a "you can redeem yourself and I can help you" thing at the climax.
2) William Burnside: They could use him, but they would probably have to drop the racist bit (or, at the very least, have him be quite a bit older). The paranoid jingoist elements, however, could be used as a echo back to the 1980s US shift to a much more cowboy-esque approach to the USSR and the rise of US neo-conservative hyperpatriotism beginning in the late 1990s and becoming the dominant foreign policy of the US in the 2000s. A outright battle between Burnside and Captain America could be regarded as a battle between theories of policy and a Captain America victory would be regarded as an end of the preemptive concept as a whole, not simply the approach. Of course, it sounds like Winter Soldier already does that, but I'll wait until I see it before I rule this concept out, as from the sound of things SHIELD appears to be simply using the New York event for development of their resources (not dissimilar to the US intelligence community in the wake of 11 September 2001), whereas a Burnside-like approach would probably fall more in line with the hypernationalism that fed off the event.
3) Sin: You know what? I guarantee Red Skull had some lover/s while head of Hydra (ego-maniacal leader of a cult of supernazis who could be regarded as the epitome of what they stood for? It would be weirder if he didn't). You could have Sin be the result of coitus, with the effects of the serum creating an abnormally strong and intelligent offspring that doesn't age after 22 (because, why not?), who takes the mantle of Head of Hydra upon maturity. Or, alternatively, you could have her as his granddaughter or even great-granddaughter, with Hyrda experiments trying to keep the Red Skull bloodline strong.
Either way, as head of Hyrda, Sin would probably be a character that infiltrates SHIELD as a prospective agent following the events of Winter Soldier and SHIELD: Uprising, as a recruitment drive to replenish dead personnel glosses over the more opaque elements of her background check. She infiltrates, moves up quickly through the ranks through her intelligence and charisma, and becomes close ally of Captain America as a team leader (similar to Coulson) or as a commander (similar to Hand), possibly even a romantic relationship. Her team and the Captain investigate a pattern of thefts of artifacts and equipment that appear to be connected with some kind of neo-Hydra organization or even Hydra itself with Red Skull at the helm. The entire thing turns out to be a ruse so that the could capture Captain America and bring him to a Hydra base for study and possibly the reverse engineering of the serum, having used the last of them to create Sin. Sin reveals herself as the actual head of Hydra at the climax, before Captain America escapes and sets off the self destruct of the base (because they would totally still have that). Sin escapes (after being presumed dead) with several of the artifacts, but the Hydra operation is so heavily wounded that it is regarded as a victory.
4) The (non-Fantastic Four) Human Torch: I can see this as a throwback to that original Stark Expo, with a brief scene where Tony Stark develops a new android based on his father's old design, with Jarvis (or some other intelligence) inhabiting the body that uses a plasma field for offensive and defensive purposes. "Yeah, I improved on my dad's old design by putting in an 'on/off' switch so it could be shutdown before the lab incinerated."
5) Captain America as a Werewolf: Eh... Maybe a SHIELD or Hydra experiment get's loose and bites the captain on the way out, requiring a search for werewolf zero (which will probably be Asgardian in nature).
6) Doctor Faustus: Would be great to help Sin recruit some SHIELD members into Hydra (see above).
7) Hate Monger: Haha... no. If there is one thing about supervillain leaders in the Marvel Cinematic Universe, it's that they all seem to prefer some element of subtlety. The hate monger most certainly is not subtle...
8) The Bradley Family: I can see this as another "Captain was gone, let's try it again" experiment, with much of the records of it outright destroyed by Bradley in the past (giving him prison time for his troubles and a reason for the Abomination to exist in this timeline). Bradley is now in a retirement home, practically catatonic and close to death from old age, while his son becomes a Vietnam (or possibly Gulf War) veteran and grandson is enlisted into SHIELD.
9) Super Patriot/U.S. Agent: Like I noted before [http://www.escapistmagazine.com/forums/jump/6.842284.20720516], Captain America was a propaganda figure, and it would be odd for the US government to just let him disappear like that. So insert John Walker as his late-WWII and early-Cold War replacement and expect a story about his time trying to be the captain.
10) Arnie Roth: I can see him as a character, possibly as an aging WWII vet or as a more recent post-thaw friend, but he won't be a driving force in a story. Unlike the time when that story was published, homosexuality is now regarded as a normal occurrence and gay rights as a given in the US and most European countries, making any story that revolves around his sexuality or partner seem way out of place in the cinematic universe. At most, I can see them as cameos in a dinner scene or possibly a pair of SHIELD suits used to emphasize SHIELD's tolerance of interoffice romance.