Why did Major Kusanagi wear a particular extreme outfit on episode 14?
(Upon review I've determined that the source provided is insufficient to support my answer. I'm currently investigating sources to come up with a more appropriate answer.)

Her body is a mass production "pleasure model" so that she blends into (I assume 'shady') environments in the city. That's why she wears sexy clothes so often, to fit her cover.

Source: Masamune Shirow via Joseph Christopher Schaub

http://schaublog.com/Writing/KusanagisBody.pdf (pg.94) [last retrieved 10/24/17]


  For his part, Shirow provides a very practical explanation for
  Kusanagi's body in the author's notes which accompany his manga. He writes:
  
  
    Major Kusanagi is deliberately designed to look like a mass-production model so she won't be too conspicuous. In reality, her electrical and mechanical system is made of ultra-sophisticated materials unobtainable on the civilian market. If she appeared too expensive, she might be suddenly waylaid on a dark street some night, hacked up, and hauled off to be sold. (1995: 103) 
  
  
  His mention of Kusanagi's body as 'a mass-production model' no doubt provides the seeds for Oshii's foregrounding of her commodity status in the film, but the critique is certainly amped up a notch by Oshii.


I've also included the author's citation:


  For all references to Shirow's version of Ghost in the Shell, the source I follow is the graphic novel. Masamune Shirow, Ghost in the Shell, trans. Frederik Schodt and Toren Smith, (Milwaukie, OR: Dark Horse Comics, 1995)