"It'd also be nice to specify that shadow and hilight colors ought to be derived from a given base color, just lightened or darkened appropriately."

Yes, that is something the standard Windows appearance dialog is able to do, and I also miss it when using 3DCC. Same as I would also like to be able to specify a font and font size for everything, and then go back and tweak the settings that should differ, instead of settings fonts and settings for like 10 different items one at a time. Maybe that would be something to suggest for ECS; !ecsMainColor (or something), which sets the 3DFace color and automatically calculates highlights and shadows (though maybe with a different algorithm than the Windows one, which often makes the color schemes too low contrast).

edit: italics seem broken again...