You've already stated they can be a means for disregarding good or evil
No I haven't. You keep misdescribing what I say.
Here is what I said - cut and posted from your reply to me!
I said that "law and chaos were presented as different means to the ends of good (or different ways of disregarding good, for evil characters)". My statement was incomplete, but the epxansion is obvious - law and chaos are also ways of disregarding good for LN, CN and True Neutral characters.
In other words, law and chaos are means towards good, or (for evil, LN and CN characters), ways of disregarding good. (Gygaxian true neutral is its own peculiar thing, associated with druidism and "the balance".)
How do LN characters disregard good? By pursuing and enforcing organisation for its own sake. They are order-fetishists. How do CN characters disregard good? By pursuing their own whims without regard to the consequences for social order and stability and the long-term plans of others. They are selfish, and potentially destructive, but not viciously so in the way that evil characters are.
what is that good or evil replaced with? A dedication to law or chaos, thus logically they are values that serve as a replacement for good and evil when those values are discarded.
This isn't logical at all. For instance, instead of pursuing humanitarianism, a person might spend all his/her time trying to improve his/her skill at tiddliwinks. This doesn't show that tiddliwinking is a value on a par with human wellbeing. It just shows that some people live silly, even pointless, lives.
Elric very much tries to change the morality of Melniboneans
But that is not an attempt to change the nature of goodness. It's an attempt to free them from error - ie to get them to turn from what they (wrongly) think is good, to what is really good.
Moral reform is a real thing, but it generally makes sense only within the framework of an objective, not a subjective, conception of value.