And in its most recent incarnation. Still more work to be done but looking a lot better:
I've managed to put the emphasis on the abdominals, as it should be. Those core muscles are what is creating that powerful gesture after all, and the center of a fighter's power-base. I used lighting and color saturation to draw attention to the torso, which is a trick I learned first from copying Tiepolo paintings, and then I also noticed Frazetta uses it. Which makes sense - if you're doing heroic paintings you want the emphasis to be on power rather than personality, so you direct attention to the torso, not the face.
I carefully modulated color saturation across the image rather than doing a global adjustment. It has a sort of spotlight effect centered on the torso/abs area, the same focal area indicated by the strongest lighting.
Added outlines almost all the way around, which I then carefully worked - making them thicker or thinner in each area as needed. This is a Frazetta thing, and I believe he did it very naturally, coming off 20 years as a comic book inker - he had amazing control over his brushes. I notice using outlines really tightens up the image everywhere - it does away with any sense of the figure disappearing into the background in places. It also gives great control over the silhouette - the curves.
Using black really increases the dynamic range and lets you get some serious punch in, in terms of contrast. So does using some powerfully saturated colors, but controlling where you put them (and using those "colorful grays" elsewhere, as Jeff Jones recommends. I think I need more of them though).
It really came to life when I added the green wrist bands - made me realize how color-starved the image was for anything cool. So I made the bikini blue, which was one of the best moves of all.