Hi Anonymous Nobody!
If an athletes association, whatever that may be exactly, led the reform, one problem would be that such would be as full of dopers as the sport, so you'd let the fox guard the hen house. Even clean athletes may be tempted to make for example the whereabouts system more forgiving, just in case they screw up.
You are also wrong about the criminalization. There is no reason to wait for the criminal process - latest example here (first banned for doping, then start of the prosecution):
German prosecutors have brought criminal charges against track and field athlete Sara Benfares, who has been banned for five years for doping, on suspicion of unauthorized self-doping.
There was also Operation Aderlass, where the investigative power of the police helped catching and banning the cheaters. Their (suspended) prison times came after their doping bans, see for example (note the timing! 7 years in Spain, lol)
The investigation was sparked following a confession by cross-country skier Johannes Dürr in early 2019, leading to arrests and raids in both Schmidt's Erfurt offices as well as during the FIS Nordic World Ski Championships 2019. Over the following months, prominent athletes such as cyclists Alessandro Petacchi and Danilo Hondo were charged with having used Schmidt's services for the purposes of doping. The investigations concluded with a prison sentence for main defendant Schmidt in January 2021....
Max Hauke received a suspended five-month sentence on 30 October 2019 from an Innsbruck court for doping violations reaching back to 2015.[10] Dominik Baldauf also received a suspended five-month sentence on 14 January 2020 from the same court.[11] Both athletes had received four-year bans from competition from the Austrian Anti-Doping Agency on 23 July 2019.[12]
Good point about the NADOs/AIU - resources would have to go to the other sports too. Clearly their built-in bias is hurting the sport (and the clean athletes), see e.g. Coleman's courtesy calls.