Sentry
I can see Seann being in the role of Robert Reynolds. I mean, he would have to gain a few pounds of muscle and grow the hair out a little but I really feel like he could own this role. Especially if they included, The Void(alter ego)
At one point in the timeline, Robert is overweight and living a day job like every else, living with no memory of his previous (superhero) life, only to keep his 2nd personality dormant. I feel like Marvel could tackle depression and maybe alcoholism if they don't touch on those subjects, in the Captain Marvel movie. Starting out rock bottom, AA and NA classes, working a crap job, struggling to make ends meet. Seann William Scott was born for this role.
For those of you, that are unfamiliar with Sentry's powers. It's basically another Superman rip off, like X-Men's Gladiator. Both have similar powers, like another Marvel character Hyperion.