This is about how much WTA would benefit from their comebacks right? Then, it's Anna Kournikova hands down. I don't think Monica's comeback would do much good to the popularity of the tour as she isn't that well known nor popular among the general public that of course includes non-tennis fans while Ann is recognized by practically anyone whether they are tennis fans or not and thus really her comeback would boost the tour's popularity immensely. The same thing as Monica's case goes about Hingis' comeback. I mean, her presence on the tour would make the tour so much more interesting and exciting but then when it comes to selling tickets, I don't think her presence would play much of a part comepared to the absence of Anna K or the Williams sisters, who seem to draw attnetion not just from tennis fans but from casual sports fans. So, in my opinion Anna should be the one WTA want the most badly out of the three.