5. Jack Flag
Captain America had a computer hotline network in the comics, through which civilians would set up patrols in their hometowns (doesnt that sound like exactly the sort of thing Chris Evans Steve Rogers would do as well?). In an Arizona town, Jack and Drake Flag were members of Caps club. All didnt go well for them, though, as Drake was left crippled by the evil Serpent Society. Finding that the local authorities had been paid off to let these snake-themed supervillains go about their nasty business, Jack trained up in martial arts to take them down. History later tragically repeated itself when a different villainous team paralysed Jack himself. Because he was an unregistered superhero, Jack ended up in a massive space prison during the superhero Civil War. When everything went tits up there, he helped Peter Quill stop a hefty collection of enraged villains. Afterwards, Star-Lord took Jack to Knowhere, where his spine was healed quickly with alien tech. He subsequently joined the Guardians. Even if Gunn didnt want to adapt this story directly, Jack Flag is a character with a rather unique look, history with the Guardians and a sense of humour too. He could probably find room for him somewhere.