There's not a single good spritesheet for this game on the net (just bad rips). I think I gave you the stuff I extracted though...?
Outlines on sprites the size of Jason doesn't work well, imo. Proportionally you're wasting a lot of pixels on lines, both internal and external, where color/values contrast between adjacent pixels would suffice to separate parts. Every pixel is precious. I recall seeing a badly ripped BM spritesheet with added outlines.
I don't think you're adressing the key features of the design. Looking at the orig. sprite and design, we conclude:
It can jump by using suspension, the wheels are not firmy attached are relative to a center node, and can be morphed/replaced with other things (in my remake: jets, legs, tracks, propellers, suction cups).
It's a tank,
...with a huge gun.
It can rotate it's turret around a center node.
Jason can enter and exit the cockpit easily via an opening hatch.
The wheels have a screw-like feature so you can tell they rotate.
It's red-pink and white.
Decorative rear wing.
(Also, the robots are grey. )
Right now your Sophia has a lot of little knobs, grills and decoration which uses up space which could be better utilized defining the gameplay relevant properties of Sophia.
Of course, one can feel free to change a thing or two, but the more you deviate, the less BM remains.
Yeah, grey can be dangerous to use for the protagonist because it's mid everything, making the character harder to spot. Red with a purple tone along with white is a good high contrast solution featuring an unnatural color unlikely to appear in terrain etc.
I'm not sure about using the more obscure images of the Sophia design as ref. The design people have been staring at is the gameplay sprite.
I'd place the turret on a ring which goes across the cockpit center.. somehow... hmm now I gotta draw that.