Anniversary is very much detailed enough, although it's based on the Halo 3 model and has a body suit appearance.

You're dead wrong about CE, though. She's got natural-looking shading across normal human skin contours everywhere. See her exposed collarbone in your images that's darkened in the depression, similar to Halo 4's? The texture has exactly the same sort of shading in other regions, and even has a belly button.

It's extremely obvious that she was intended to have a naked appearance in the first game, and they possibly backed off from this with Halo 2 due to the more realistic visual style.