In an open chess tournament, they just have "rating" categories, and give out prizes for the winners of each based on past performances. If they did the same thing for athletics, it would not only get rid of the dispute over deciding who can be classified "female", but it would also encourage more participation by introducing categories for people who are newer to the sport and are not competing at as high of a level. Just base the prize/award categories on PB in the last and current season. When you register for an event, you can choose your category to compete in based on your past or current season PB. If you've never raced that event before, then you can choose any category.