Seems like a fundamental misunderstanding of the series. The idea is to show that you can't just go batshit and break bad in life in such an extreme fashion without some dire and very permanent consequences to your actions, and that it's a one-way road. There's no redemptive arc to be found here, and there's no way for this show to keep going without Walt only continuing to sink deeper into the abyss. The only thing that remains to be seen is how many people he takes down with him before the end.
If Skyler were to become hooked on meth, it wouldn't change much of anything. Walt's defense mechanism is to rationalize every horrible thing that happens on his way to Empire-ville, and it would be the same there.
