But could Michael Shannon *fight* in that suit? I doubt it.
At any rate, you might be jumping to conclusions a little too quickly. Yes, we know that Zod's armor will be CGI in the fight scenes, but I think his armor will be real in the nonphysical scenes. If you look at the picture released by Empire magazine, the suit looks very, very real. I don't think it's CGI:
This approach (i.e. real suit for dialogue scenes and CGI suit for action scenes) is certainly not unprecedented. The Iron Man movies are shot in exactly the same way, from what I understand.