A good NASCAR roadcourse is a sweeping course, with space to maneuver with inclines and dips. I don't think street tracks are compatible. Although I must admit I'd be curious to see them run somewhere like Cleveland airport!
A Dirt round would be great.
I think retain most of the epics. As long as the cars are racey there isn't a problem. Some of those 80's and 90's races where real action-packed epics, and the hours flew by. I think there is something more fundamental with COT than tinkering with race distances will resolve.
As for international races they could do a small tour if the price is right.
Like Knockhill for example.