In a dream world: find a law firm that buys the class action from you. Given their market share and the amount in question, it should be a profitable affair.
Meta-idea: create a startup that functions as a marketplace for bringing together ideas for class action lawsuits and law firms.
Not quite the same thing as what you mentioned, but by creating financing that evaluates cases by their potential for a payoff, this should seed the kind of marketplace you mentioned.
Meta-idea: create a startup that functions as a marketplace for bringing together ideas for class action lawsuits and law firms.