DC character would he be perfect as?

He's getting a bit old to be Superboy, considering Henry Cavill who plays Superman is only a few years older than Aaron. Apart from this, he's probably signed a contract with Marvel that prevents him from playing character from a comic adaptation from a rival company, particularly DC.

Always thought he was one and done

I don't know. I think those contracts are multi picture ones. Even if his character is not meant to return that doesn't mean he cannot do it. It's a movie after all. If he's signed a contract with Marvel I doubt he can get out of it that easily without committing to more films.

That's messed up only appearing in one and unable to go anywhere else afterwards

He can, he just can't do a superhero/comic adaptation from a rival studio. I'm not sure what his contract with Marvel stipulates, but he may have signed on for three movies maybe. But he's free to do anything else. On the following interview he states that he cannot say how many movies his contract attached him for. He says he can't talk about it, so who knows, maybe we'll see Quicksilver again.

http://www.comicbookmovie.com/avengers/avengers_age_of_ultron/aaron-taylor-johnson-talks-his-deal-with-marvel-a120355

I wonder how long he would be under contract for. Ben Afleck did play Daredevil (Marvel) before playing Batman (DC). But of course that was 13 years ago. But, more recently, Ryan Reynolds played The Green Lantern (DC) before Deadpool (Marvel) and that was only 5 years later. Do you think maybe the circumstances are different because both actor's first hero movies flopped so poorly? I hope what I'm asking makes sense...

Tim Drake

I guess it depends on the studio wanting to do more sequels/adaptations. If Green Lantern had been a hit, there'd had been a sequel and most likely that would have prevented him to move on to Marvel. Only a few years before Green Lantern he was in one of the X men movies wasn't he? I guess they didn't need his character anymore so he was free to do Green Lantern.