I just rewatched Mean Creek yesterday. Great little indie drama. Amazing performances by a few young actors. But, of the bunch, the most impressive is Scott Mechlowicz. I've pushed for him before, but I'm gonna throw my hat behind him even harder.
The guy can easily do comedy, as he did in Eurotrip, or he can bring some intense drama to the table, ala Mean Creek. He's 29, which is a little old for Bucky, but he can play much younger. I mean, in Hollywood, that's no problem. (In Ferris Bueller, Alan Ruck was 32 when he played high schooler Cameron).
So yeah, Scott Mechlowicz for Bucky. He can bring intensity to the battle scenes and comic relief when needed. Exactly what Bucky needs.