Lex should be an evil genius. Having a large corporation works too.
Not really feeling Mathew Fox...
Guy Pearce could have worked but IM3 has him.
Daniel Craig I think would be avoided by Snyder and co. just cause he's so ubiquitous as Bond.
Brad Pitt is probably too high profile but I think he could make the role very 'cool' similar to Heath Ledgers Joker, if he played it similar to the Tyler Durden towards the end of Fight Club. I'm not saying Luthor should be 'cool', I just can picture Pitt portraying Luthor at the end of All-Star Superman where he's high on Supes' powers and has his view-changing epiphany.
Overall I'm undecided and based on what we know Luthor casting is what they will tackle should we get a sequel. We'll have to have our eagle eyes on during the Metropolis scenes for any 'Lexcorp' insignia to give us an idea of what Luthor they'll go for.
I think the sequel could have a TDK vibe with his Kryptonian roots covered in the first film it can focus on his worst enemy as a sort of master manipulator like Joker was in TDK. Have bombs rigged all around the city, give Supes moral dilemma in trying to reach them all with Lex setting them off with different impossible choices (similar to saving Rachael or Dent). Obviously there's more than bombs and explosions that could be used. If Kryptonite is not introduced in MOS I'm sure Luthor will have it in the sequel. Have Supes shaken too his core and questioning his mission. We don't need a villain as powerful as Darkseid to up the stakes.