The more I think about it the more I think that this would make a really good game. Not only do you have the whole of Earth to play with, with the ecological concrete nightmare it has become, you could take the game off-world to the colonies.
The game would be driven by investigation, not just Blade Runner units but maybe normal law enforcement or government/corporation agents. You'd have the normal Replicant-hunting games, chasing after different models for different reasons and all the existensialist and moral dilemmas that incurs, but you could also have investigations into normal, everyday crime, and even tech-crime you find in many cyberpunk-type games. The added bonus is that you have the very definitive atmosphere that Blade Runner offers - you're not trying to emulate it in a Gibson-inspired game but actually live in the world that Blade Runner presents. If you go off world you could even mix the two genres that Ridley Scott helped visualise - what's stopping Weyland-Yutani from the Alien franchise being in it, or at least a version of that company, and the type of interplanetary travel could be Alien/Outland inspired? That way you could keep the dirty, used industrial feel of the original movie and not lose the atmosphere, which is what the original tacked-on studio ending did to the original Blade Runner release (if there were great swathes of forest to escape to, with sunshine and trees, what the hell were people doing living in that crappy crumbling city?)
You'd need basic rules, of course, a detailed description of the setting using stills from the movie, or at least artwork inspired by the movie, and stats for very few extras. Deckard's gun, for one (how cool would it be to pull that baby in the heat of the gaming moment?), the abilities of Replicants (which won't be far removed from standard human stats, anyway, and maybe you could have a random emotional reaction table when something stressful happens to them, which makes them unpredictable - could you imagine playing such a character?), off-world colonies (you don't need hundreds of pages, just enough to let the players know that travelling there is a possibility), spinners (cars that fly - how difficult can it be?) and possibly starships and spacestations and any extras that the setting would require, maybe taking elements from Scott's movie, Dick's original novel and Jeter's sequels.
It'd be an excellent setting. If Cyberpunk 2020 and Shadowrun can produce years of material using the imagery of Blade Runner then I'm sure that Blade Runner itself can do it.