[Geass]

I was going to say her figure looks better in the 2nd pic
In the 4th pic she looks like a freaking stick with breasts

Not to draw comparisons, but if you ever seen "Triplets of Bellvile" the illustration style is a very exaggerated style. Since One Piece has many characters going through Super Deformation, you take in consideration that maybe the artists are just forgetting where they started with, or are maturing their characters as they go. Maturing meaning as in physical "Maturing" as well as the character design.

Note the 4th picture as you pointed out, you could call it an exaggerated hourglass figure, while the last one you could call it a matured exaggerated figure.

Figure scale:

Exaggerated figure: Triplets of Bellvile
Realistic exaggerated figure (i.e. Fanservicy): Tenjoh Tenge
Realistic figure: Ghost in the shell or other realistic anime, such as Macross Zero


Then comes style which I think what One Piece fits in that catagory.