I see no good way to make new bikes competative against old bikes. A modern 400cc dual sport is just too good of a machine, SO, it will once again showcase older stuff. 20 years old or older. I will say, I am REALLY tryng to think of challenges that give the streetbikes the advantage. All challenges in teh apst have given offroad machines the edge. Maybe more paved road sections for the timed legs.
One way or another older bikes will be featured. Fixing up Barn built bikes is kind of the point.