"the real answer would be not to forbid people from supplementing, but instead to pick some acceptable level of beneficial metabolic processes and let everyone

"the real answer would be not to forbid people from supplementing, but instead to pick some acceptable level of beneficial metabolic processes and let everyone get themselves to that." that's basically how a lot of doping testing works. They don't know where the testerone comes from but assume that people will be within a certain range. In cycling they called Bjarne Riis "Mr 50%" because his hematocrite level was always exactly at the maximum allowed level. Read Tyler Hamilton's book. It's a good read and gives a lot of insight into how doping works.