This kind of testing is already done in certain contexts. I am thinking specifically of air quality and automobile efficiency standards which are "tested" in California before being rolled out to the nation. However, this is only allowed because California has special exemptions from federal law in these contexts. It is important to note that scale and scope are critical-what may be efficient/optimal in one locale may not be so in others, or at larger scales. E.g. fuel standards and national energy profile are arguably under legitimate federal authority... other issues not so much. Also important to point out that the "optimal" and "efficient" are not mutually inclusive or absolutely defined-preferences, for better or worse, are king.