As I said, the problem is writing the tests and knowing what to measure. How do you discern between a bunch of tests and measurements that are poorly-designed, and a bunch that are well-designed? You gather a bunch of people with good taste, and trust their gut.
But at that point, why not just cut out the middleman, forget the tests, and let the artists be artists?
See also: Footnote 3 of http://www.paulgraham.com/colleges.html#f3n
...for now, given today's technology, but I wouldn't bet on it long term. History is full of examples of things we once thought only humans could do.
But once many candidate designs are available to choose from, what better a way is there to unambiguously decide on the best besides testing and measuring?