I'm not sure this is possible. But, Personally, I would avoid doing this.
For a variety of reasons.. But, mainly, if a client requires a specific CTB for a project, the lineweights would be jacked in the final product.
Internally, you could get around this by using layer dependent plot styles or STB but the moment a client would require a specific CTB be used you would have to then revert back to the standard ACI which would still make changing anything moot.
If you are looking for a specific color/shade I recommend using a true color variant and edit the shading as needed.
It sounds like your question is a color related question to autocad, specifically, not anything involving lineweights.
But your lineweights would still be affected in the long run and cause potential headaches moving forward.
-ChriS