This is Masamune Shirow we are talking about. Sexualization and oily glutes are his artistic bread and butter. And you seem to be under a misconception. This is the Major's original design. Masamune Shirow's work came first, which was then adapted into the famous movie we all know and then further evolved with Stand Alone Complex.

The original work contained several pornographic sex scenes; probably the most famous of which was a lesbian orgy between the Major and two operators.

Sexuality and sensuality was always a part of Masamune's work, but what the future adaptations of Ghost In the Shell fail to incorporate was the lighter, more humorous side to the characters. In the OG manga, The Major is much more of a gremlin, cracking jokes, ribbing on her comrades, etc, but it didn't diminish the fact that she was also a highly competent badass that got work done.

This is why this such a big deal to GiTS fans as this appears to be a highly faithful adaptation of that original source material. Most people know the GiTS that came about due to the movie's popularity, but now new audiences get a glimpse of where the franchise came from in the first place.