I would have no issues with Cranston as Lex (or Mark strong either) and the age isn't a problem either because Lex has been depicted as being the me age as Superman to a few years older to being old enough o be Superman's father. So the casting of Luthor could range from early 30s to around 60ish.
I still personally think Matt Damon would be a good casting choice if he would be open to taking the role.
I still personally think Matt Damon would be a good casting choice if he would be open to taking the role.