3dJoes.com has a great feature about the pre-production work on Scarlett, including the original character sketch by Ron Rudat:
The piece is labelled "Master of Stealth Weapons," and in addition to having a few sample pieces of comic art to show what he thinks he face should look like, the drawing is annotated to point out her shooting vest, padded shoulders, the armor plate below her belt, the fact she keeps "extra ammo + etc." in her boot-pockets, and more.
It's interesting to note that even at this early point, Ron was aware that when the figure went into production, she wouldn't be able to have long hair: instead, she wears her hair in that fancy braid. That said, this drawing was submitted in May of 1981; does that strike any chords with you? Like, the hair, the padded vest, the boots... do you see it? That's Hoth Leia! He drew Leia as she appeared in Empire Strikes Back a year prior as the starting point for Scarlett!
(Also notice that the gun she's cradling in her arm looks like the fully kitted-out Man from UNCLE gun - a GI Joe/Transformers crossover before either GI Joe or Transformers were a thing!)
Two months later, the character had progressed to the version we know today:
If you've ever wondered what all the things sculpted on her were, the notes will make them clear.
And as promised, here's Larry Hama's original file for Scarlett, including her official job description of "Girl":
("R. Carosella" is a reference to Robbie Carosella, a Marvel colorist at the time.)
So you mix a little bit of Princess Leia and a little bit of Lilah "Shadow" Galil from Fury Force, stir vigorously, and bingo, you've got yourself a Scarlett!