Whenever I hear talk about an athlete’s union, I think it’s a bad idea, not inherently—I am personally very pro-union—but logistically: too many athletes’ careers are either too short or can’t even be defined as a career as such (as they’re more high-level hobbyists with a day job that pays the bill), and there are too many different disciplines and event groups with different needs and goals for the group to ever present a united front.
The thing that strikes me as more plausible is some form of athletes’ group forming, or having a seat at the table to determine the structure of, the domestic professional track tour. If one of these “Professional Track Athletes Association”-type organizations collected dues (and, not to get too greedy, but maybe a little bit of sponsorship money) with the goal of putting on a domestic circuit with meaningful competition opportunities and prize money, and then used those membership fees to hire a professional team to produce a (or, ultimately, a series of) meet(s) that met those goals (meaningful competition and substantial prize money), that seems an achievable, common goal.
Of course, that may be less-necessary now than it was a couple years ago, as some of the more athlete-oriented meet organizers have come together to start building that domestic professional circuit. But having formal systems in place to give athletes a voice (although not necessarily final say) in decisions about those meets doesn’t seem like a bad thing.