How about just standardization within one brand? Chanel is all over the place even in the same season. I agree that measurements are the way to go and some websites actually post them for a garment and that is very helpful.
That's why I love sites like net-a-porter, matchesfashion, forward, etc. because they make meaurements available for individual garments. I wish department stores like Neiman and Saks would do the same.