I'm not convinced that Christians just want to see more Christians on TV. Rather, they want to see Christians portrayed on TV in a positive light. Modern TV shows (like
Breaking Bad) are about exploring the moral assumptions we make about ourselves, and are often skeptical of objective morality. If a major Christian character were included in
Breaking Bad, the show would have to make a choice about whether to portray that character trait positively or negatively. But
we've already seen how the show portrays characters who purport themselves to be guided by strict moral compasses. The mustachioed twerp in this clip repeatedly espoused quasi-religious messages of forgiveness, but all this does is make him look hopelessly naive in the show's world.
Simply put, it would be hard for a show like
Breaking Bad to portray Christians in a positive light, and even if it did, then it would come across like it was shilling for Christianity. So the answer is to just not address it at all (not explicitly, at least). And quite frankly, putting a Christian character in the show who actually acts morally would ruin the entire point of the series.