After only just now reading a TotalFilm interview with Drew Pearce, I think it could be a great way of developing Rumlow's evolution with a One-Shot.
After AHTK, these could potentially be a great way for Marvel to do this with other characters that don't necessarily need a full length feature.
What other One Shots had you written that didn't quite make it to fruition?
DP: Oh, gosh - lots of them. One that was Sin and Crossbones (from Captain America).