The TK have always has some of the most powerful magic in the warhammer world. Everyone else was getting updates, why not TK? Also, as for thinking that bigger Bone giants would be better than a Sphinx, or a Legitimate sphinx?? (no idea what you mean) I have no idea what you mean. So the current line was better because it was the current line?
Also, remember that the studio painter CHOSE to paint them as having black onyx or whatever, you can easily paint it in another manner, make it look more stone or however you wish.
How are the snakes any more complicated than the scorps are? One 'works' the other doesn't? Doesn't make any sense. So maybe a unit here or there is not your cup of tea. My understanding is that core skeletons went down in price and TK chariots will be solid. So it will still keep the classic elements intact.