Well instead of going 'balls out' and opting for a 'global' look why dont you try this with a couple of spots first just to gauge the look you're after. You'll be able to see how intense the overall light and shadows contrast against one another

Global/sky/fg all produce an overcast effect in their 'default' settings, itsa trap that most people fall into, and regardless how much you crank up the settings its going to look flat unless you add lights to the scene.

Personally I'd put one light in the scene as your main source, this means for shadows too, then once you are happy with the direction of your lights then begin to add in your FG/GI etc after for more of a 'fill effect.

you can then begin to tone down the main light if you want or keep the FG/Global settings to a minimum as well so you have a balance of the two.

Have a look at the sky settings anyway in the help docs as it comes in with a directional light so its a case of having a read moving things around and looking at your settings.

I recently finished the Sand Speeder tute here, it has rendering in it using fg, but I still used 4-5 spotlights to finish the render off....

Jay