I tried doing something like that with the gray wood recently, but it's going to be immensely hard to pull off effectively without changing the relative saturation of everything else in the pack (most video games also have a lot more control over specularity of materials, which helps). At the end of the day, I see us as basically having made a stylistic decision (in the tradition of the original Dokucraft) to make our textures fairly simple and a bit more "cartoonish" than uber-gritty-realistic, differentiating us from other resource packs like Conquest. I see this as similar to the use of Cel shading in some video games (such as Legend of Zelda); the textures aren't very realistic and the colors are very saturated, but the worlds (relative to someone's subjective preferences I suppose) are still visually beautiful and fun to explore.
EDIT: also, for the record, I think a truly realistic texture pack is going to be impossible to pull off in MC without the full control over materials that's offered by most game engines, i.e. specularity, bump-mapping and the like (although I think Optifine does put in a hack which enables bump-mapping, I haven't seen it used in any major packs yet). While Conquest textures are made by a super talented team of artists, I find that the noise and detail of the textures detracts from the actual worlds people are trying to create with it.