Re: Looking for a miniatures ruleset
You can use generic minis with Space Hulk rules. I've played it with Heroscape figs for example.
Outside of that, look at Flying Lead or Mutants and Death Ray Guns from Ganesha, or Chain Reaction and the related games from Two Hour Wargames.
Chain Reaction is free, the various genre specific books are not. Try out CR to see if you like the rules, then pick one of the specific books that suits your topic.
FiveCore Skirmish rules from Ivan Sorensen would probably also fit the bill. Just picked those up (bought the FiveCore and No End in Sight bundles over on Wargame Vault) and haven't actually played them yet but have been reading through them.
The Spec Ops module for Gruntz 15mm is also aimed at a fairly small number of figs.
And of course, take a look here: http://freewargamesrules.wikia.com/wiki/Freewargamesrules_Wi...