So often I find that there are certain tools in the toolbar that I just don't have a lot of use for/only come up once in a blue moon, and I think with the new multi-document feature, this would be more than just a creature comfort.

It would work by allowing you to have all the tools you don't want on the bar in a "chest," and that would include the colors as well. Since you can drag and drop all the UI elements, you can essentially customize your UI to use the least or most amount of space possible!

Use single documents often? Just have all the tools out in the bar like they are currently

Dual-Screen Documents? Hide your least used tools, now you have less resizing to deal with!