One great Edward Elric in DC fanfiction is 'The Alchemist in Gotham'. In this story, Edward's alchemical skills bring a unique dynamic to the DC universe. His no - nonsense attitude and determination to do what's right fit well with the morally complex world of DC.
There's also 'Edward Elric: DC's Unlikely Hero'. It shows how Edward, being from a different world entirely, has to adapt to the strange rules and powerful characters in DC. His character development as he tries to find his place among the heroes and villains is really interesting.