First, I just want to say that I get wishes are probably most likely a last-ditch effort by bungie to keep us busy until new content drops, but what if there is more to them? Through the season, we've seen Crow, Petra, and Mara all talk about how they want to save their people from the Curse and they realize that the Dreaming City itself is most likely lost, but maybe the people themselves can be saved. Then we got Rivens wishes, which according to Mara seem odd and requires us to complete random tasks. She finds no ill intent or alternate motives behind them when she screen them. So what if as a thanks for ours, Petras, and Crows hard work she designed a series of tasks which individually mean nothing, but together exploit a loop hole in Savathuns wish and free the Awoken people stuck in the wish. This could explain the random nature of the tasks as well as the wish tokens which appear to be Rivens teeth. Perhaps by completing each objective, we charge of the token by filling it with paracausal energy, and once enough are charge up, maybe it can temporarily bring back Rivens spirit so she can grant 1 final request. I mean she did offer to help Petra free her people, if she only wished it so and Rivens spirit only faded away because of the amount of power she needed to grant the 15th wish.