Before i start let me say that I love the idea of the character. I just think that some tweaks should be made to make the character more of an interesting read. For organization, I'll just do it all in bullet point form.
- Weaken him: Don't make him immune to human weapons, just have him being very powerful against them. ex: A magazine from an M16 fire straight at him should at least bruise him and slow him down some.
-Lose the powers: X-ray vision? Heat/ Laser vision? Ice Breath? Really? I say lose these powers. Go back to the days when Superman got all of his powers because of our sun which enhanced his normal abilities. The few i mentioned above don't really make sense when looking at in that perspective. Hey maybe even turn it back to being able to leap buildings in a single bound! Now i'm not saying these must be permanent but maybe start him at ground zero and work him up again SHOWING how he got these powers and how it makes sense that he has them.
-Mortalize him: This is in the character sense, nothing physical. Have him lose once. Batman loses a lot but he always survives. Do the same for Superman. Have him lose someone and have that haunt him. Make him grieve, make him challenge his ethics. Make him human.
Honestly i just think Supermans gotten too super as of late and writers mistake having a bad*ss enemy for having a good story. Take him back to the golden age. Morrison started doing it in his first run on Action Comics. It doesn't have to be so severe as whats mentioned above. But seriously, hasn't it gotten kinda ridiculous?