This is counter to your thesis. Messi's dominance doesn't come because he has elite physical characteristics. He's dominant because his level of skill with the ball at his foot is an outlier even among elites. It's not because he's pushing the physical limits of the human body.

There might be some variance in skill for elite riders, but I would guess the density curve of skill in that cohort is a very narrow bell curve, ie. low variance with relatively few outliers. This is what I mean when I say pure skill is not the major factor in success in cycling. Most riders are going to be pretty closely matched skill-wise, and the winners are going to be those that can generate the most power for a sustained amount of time.