Yeah I think the AU and Secret Origin versions of Metallo are pretty fantastic. The latter is more fleshed out and more adult, which would make for a (somewhat) sympathetic villain while also just being an all around brutal creep, especially with his connections to Lois and Sam Lane. It cuts a little close to that annoying Talbot character from the Ang Lee Hulk movie but way better and obviously a live action version could be very cool visually.
As for an actor to play him, along with Dickinson, I could also see Alan Ritchson in the role. I would probably prefer to save him for Captain Atom but for Metallo you need a big, imposing, cocky military alpha male type.