No, this isn't another "should it be simplified/expanded/retconned/rebooted" topic. It's just a simple thought exercise. The idea is to take a theme or style and rebuild the setting (possibly the rules, if you feel it necessary), showcasing that particular style.
A simple example, using the cyberpunk genre or theme.
Battletech: A Game of Cybernetic Infowar Combat
It is the dawn of the 32nd century. The Word of Blake's Jihad and White-Out virus have brought non-"wetware" technology crashing to its knees. It almost brought our entire race to the brink of extinction. The technology we depended on to survive has failed, spectacularly. Our might BattleMechs have fallen silent, and the guns of our WarShips ring out no more. Until Stone, and his damned crusade. He delved deep, far deeper than we ever should have allowed into the Star League's hidden technologies. Caspar drone network architecture, mega-engineering super-factories, automated cascade firewalls...it was all grist for his abominable millwheel of progress. We've been ground to dust beneath it. We've survived, but we'll never be what we once were. Human.
Welcome to a world of cybernetically enhanced foot soldiers, brain-linked Mechwarriors and Aerospace jocks, and people plugged into a virtual world of information and entertainment. Welcome to a place where the future is now, and that future is here to keep you from looking outside the window of your blighted bio-dome arcology. Don't look to close, or breathe in that outside air. It might just be fatal. Most of us exist to serve our corporate and noble masters, fighting for half-dead worlds and limited resources, plugged into ever increasingly intelligent machines that seem to control more than we do ourselves. Are we all just part of some great System? Are we really just the Ghosts in the Machine and the world has already died? Some days...it's damned hard to tell.