Choosing a framework for Project 5.5

So...my first (next?) step for Project 5.5 shall be to decide upon a ruleset that can serve as a framework for the sort of "miniatures" battles I want to stage.  I have some in mind already...and am having a tough time settling.

In short, I'm looking for rules that are...

1.  Fun to play.
2.  Functional with minimal paperwork (since it'll be played outside).
3.  Capable of capturing the somewhat gonzo science fantasy flavor of Masters of the Universe.
4.  Usable with teams of 3-6 figures per side; ideally it would work (and retain its playability) with as few as one figure, up to maybe dozens.
5.  Able to make use of these great D6s Laura gave me for my birthday last year.  (I have six of 'em.)

Tulip is just there for scale.

I hope to get some posts up this week with some of the options I see as top contenders.  In the meantime, please feel free to suggest away if you have ideas!