I've never supported co-washing. We would never cleanse our skin with lotion/moisturizer so why do it in our scalps? The scalp is just an extension of the face, it functions just like skin everywhere else.
My shampoo has one sulfate (Yes to Carrots) a soup of them is really not needed. Diluting the shampoo with water (per use, not in the bottle it comes in) is also an option, which is what I do. But I'll never understand co-washing only or adding oils and such to shampoo. I can't wait until the natural hair community stops touting this and teaching newbies harmful methods.