I like this idea because I've had a similar solution in mind when it came to browser inconsistencies (not that this is a solution, but it could be). One major problem with the advancement in browser technology is one, leading browser's lack of force behind the user to upgrade their browser to the latest version, from my observation.
Quick thought, what would happen if every website today refused IE6 as a web browser and commanded the user to upgrade to IE7(or latest version of IE); or if the user is running an older version of Windows, say 98, then recommend Firefox 2? What could happen is users would need to go out of there way to hack that system if they love IE6 so much, or go less out of there way to upgrade their web browser.
I'd like to hear your thoughts(Yeah, reading minds would be cool).