Hi there.
Ah, Macho Women With Guns, what a fun beer & pretzels game - if only you have a group of players who get the jokes. I have two of the earlier incarnations of that game, from 1989 and early 1990s. It originally used a roll-low D20 mechanic, and IIRC the second edition had a 3D6 system instead, very similar to GURPS.
I cannot comment much on the Saga Edition. I only know it was created for Star Wars and streamlined a lot of details, like starting skills etc., from the D20 system material. I guess parts from SW Saga Edition could easily be ported to other franchises and settings.
Personally, I wouldn't want to try adapting MWWG to RuneQuest, for the reasons stated already. RuneQuest is tailored to pure, gritty fantasy. MWWG also does not need something as fine-grained as a percentile system, so the steps on a 1-20 scale seem a lot more appropriate for its style in general: D20 instead of D100, you know.
As for the classes in MWWG, or templates or archetypes if you prefer to call them that, those were actually explained nicely in the first edition, where there were only three of them: Macho Women, Demonettes and Killer Nuns.
Villains & Vigilantes? Hmm, why that? Is that easier than a d20 derivative? I believe MWWG would be suited to a stripped down GURPS, Unisystem, Fuzion, or to the True20 system. I could probably list more.