Alright, Giancarlo Esposito, I'll take a shot at guessing who your character is in Captain America: Brave New World

In case you missed it, Marvel released the first teaser for Captain America: Brave New World. Here's what that looks like:

Following the teaser, there has naturally been a lot of speculation about who the mystery character is that Giancarlo Esposito is playing in the film. A popular theory was that it's one of Rob Liefeld's characters, named (sigh) George Washington Bridge, or GW Bridge for short. But Mr. Esposito himself has said that no one has correctly guessed his MCU role.

I guess I'll have to take a shot at this.
So, here's who I think he might be playing.

James Bourne (a.k.a. Solo)

Now you'll notice that Solo is depicted in the comics as Caucasian, probably in his 30's, and wearing a green super-suit with one of those weird half-open head socks that Marvel loves so much. And Giancarlo Esposito's character in the film doesn't fit that description. Although, who knows what else he'll end up wearing in this movie.

Solo (Vol 2) #1
Pencils and inks by Paco Diaz
Colors by Israel Silva

But I can think of three reasons (which make sense to me, dammit!) why Solo could be in this film.

1. He's an ultra-spec-ops soldier who was done dirty by the U.S. government. They could just say that his ill-fated Omega Strike unit was one of General Thaddeus Ross' pet projects, and -HEY PRESTO!- you can already see how he might take issue with Ross running for president.
2. His backstory includes manipulation and betrayal. And we know another major villain in this film is Samuel Sterns (a.k.a. Leader) who spends most of his days trying to overthrow the U.S. government by means of manipulation and betrayal.
3. Solo can teleport at will (albeit with some limitations), which helps make him a threat to the two flying protagonists.

Also, Harrison Ford being in his 80's, maybe that's why they didn't want a 30-year-old for this role. It could be that the story they're going for is that Esposito's character (whether it's Solo or someone else) has an old wound that gets torn open when Thaddeus Ross runs for president. And Samuel Sterns is exploiting that.

I guess we'll just have to keep our eyes peeled for any teleporting by Mr. Esposito.

PS.
I would have cast Giancarlo Esposito as Norman Osborn, but that's just me.

Update

It was officially revealed that Esposito's character is Seth Voelker (a.k.a. Sidewinder), the leader of a superhuman criminal/mercenary group known as the Serpent Society.

Coincidentally, Sidewinder also has the ability to teleport!

I think I deserve half a point for that.

Official Handbook of the Marvel Universe Master Edition #14
Pencils by Keith Pollard
Inks by Josef Rubinstein
Colors by Andrew Yanchus