You got the idea man!
We've got grand stands, announcer's tower, advertisements, etc.
I'm thinking combining 'train modeling' techniques with 'bit track' building techniques would render some awesome tracks. The buildings, grass, hills, roads, etc. so much detail, that'd be friggin' too cool!
Now, what can we use for an oil slick or ice patch?
Love your idea on blocking off streets too, I'm already imagining a scene from the Fast and the furious!

Using those cross-sections of streets, theoretically, you could block off certain streets to make an entirely new course on the same track!
Oh man - now that'd be awesome! You've got my mind reeling now.