2. Swordsman
In the comics, Clint Barton was trained by two men back in the day. One of which was a man named Jacques Duquesne, better known by the name Swordsman. Jacques has a long, tangled history. He was mostly a bad man who wanted to do good. I think it would be cool if the show took a few liberties with him. They could have him as one of the, if not the only, people to train Clint pre-S.H.I.E.L.D. They could get an older, but still, kick butt actor like Pierce Brosnan or Charles Dance to play him. I imagine him and Clint having a similar relationship to how Matt and Stick were in Marvel’s Daredevil. They could even parallel the story of passing the torch by including Jacques’s daughter, Adelynn who could be frienemies with Kate. I see Kate and Adelynn having a similar relationship to Matt and Frank’s also in Marvel’s Daredevil. They could even use Adelynn and maybe Jacques in something Thunderbolts related.