If I can reimagine any existing character, then my vote goes to Bucky. Basically because I want to see Sebastian Stan as a gay man
That would fit. Since they've both been frozen, essentially time traveling to the future, Bucky could realize that the fondness he felt for Steve was more that a bromance.
That could work really well.
And my main vote would go to Captain Marvel largely because she'd be a new inclusion to the universe, a main player, and one of the strongest heroes. The downside is that some people would say that we're equating lesbians with masculinity. Fuck 'em.