Before you go to a popular game engine for your next campaign and you spend an age tearing the system up to make it work for what you have in mind, can I just point out that there is a system with which you don't have to do that to a huge extent.
The MiniSix system is a cut-down version of the D6 system that covers all genres, is modular so that you can make it as light or crunchy as you want, is easy to hack and really easy to learn. Its basically the WEG Star Wars D6 game (I've always said that the first edition rulebook worked well as a generic system) trimmed right down for general play.
The D6 System is well worth your time and a lot of fun. Before you hack into your usual system, give this a look.