Proficiency is already required for all retired law enforcement personnel who wish to carry concealed (in all 50 states, at least according to the law) under HR 218. Although there is some variety in the different qualification courses, they don't seem all that difficult to pass.
That being said, the more government involvement in anything, the more difficult and confusing it gets. Plus, I have long believed that the only reason governments have requirements for permits, licenses, and so on, is so that they can tell some people they will NOT receive permission to engage in a behavior, or receive something they want. For example, although the purported reason for a license is to ensure that people have sufficient skill to operate a motor vehicle, there are a great many people who have sufficient skill to operate a vehicle WITHOUT a driver's license. Government just wants to tell some people to NOT operate a vehicle.