If you are willing to go outside d20 Mekton (I use Mekton Zeta) is good. Otherwise I recommend either d20 Future if you are familiar or Mutants and Masterminds for its flexibility and being relatively rules light.
If you are willing to go outside d20 Mekton (I use Mekton Zeta) is good. Otherwise I recommend either d20 Future if you are familiar or Mutants and Masterminds for its flexibility and being relatively rules light.