and have it follow the world's rules,
I think this approach to game design is horrid. Part of the fun of video games is that you don't have to follow the worlds rules! Make something that acts wacky and doesn't make sense in the real world ... stop trying to replicate what we've already got!
I know quite a few people who are trying this approach of shared media with coded rules so that anyone can set up there own little virtual world and have it react correctly. For the most part I think this sucks because it means games are converging into one single boring experience.
Of course mixing some standard features with your different ones does make sense on some level ... but you know it's going to end up making even more clones than ever.