Now, I don't mean ALL sides are unique, just the top, sides, and bottom. I know this would break a lot of the pre-existing texture packs out there that aren't being updated, but I think this would be awesome to have regardless. Reason is, I know of a couple Zelda related texture packs out there, and being based off the 2D games, they have the traditional "cake layer" texture for stone or dirt. But this looks funky when all six sides of a block have that texture.
Even without Zelda texture packs in mind, this could still allow for more creativity when creating new looks for Minecraft.